diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/Feature.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/Feature.kt
index ea22bdfb..cb7977ab 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/Feature.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/Feature.kt
@@ -32,8 +32,8 @@ import kotlin.jvm.JvmStatic
  */
 @Suppress("TooManyFunctions")
 @Serializable(with = FeatureSerializer::class)
-class Feature(
-    val geometry: Geometry?,
+class Feature<out T : Geometry>(
+    val geometry: T?,
     properties: Map<String, JsonElement> = emptyMap(),
     val id: String? = null,
     override val bbox: BoundingBox? = null
@@ -80,7 +80,7 @@ class Feature(
         if (this === other) return true
         if (other == null || this::class != other::class) return false
 
-        other as Feature
+        other as Feature<*>
 
         if (geometry != other.geometry) return false
         if (id != other.id) return false
@@ -115,26 +115,27 @@ class Feature(
             )
         }}"""
 
-    fun copy(
-        geometry: Geometry? = this.geometry,
+    fun <T : Geometry> copy(
+        geometry: T? = this.geometry as T,
         properties: Map<String, JsonElement> = this.properties,
         id: String? = this.id,
         bbox: BoundingBox? = this.bbox
-    ): Feature = Feature(geometry, properties, id, bbox)
+    ): Feature<T> = Feature(geometry, properties, id, bbox)
 
     companion object {
         @JvmStatic
-        fun fromJson(json: String): Feature = fromJson(Json.decodeFromString(JsonObject.serializer(), json))
+        fun <T : Geometry> fromJson(json: String): Feature<T> =
+            fromJson(Json.decodeFromString(JsonObject.serializer(), json))
 
         @JvmStatic
-        public fun fromJsonOrNull(json: String): Feature? = try {
+        public fun <T : Geometry> fromJsonOrNull(json: String): Feature<T>? = try {
             fromJson(json)
         } catch (_: Exception) {
             null
         }
 
         @JvmStatic
-        public fun fromJson(json: JsonObject): Feature {
+        public fun <T : Geometry> fromJson(json: JsonObject): Feature<T> {
             require(json.getValue("type").jsonPrimitive.content == "Feature") {
                 "Object \"type\" is not \"Feature\"."
             }
@@ -143,7 +144,7 @@ class Feature(
             val id = json["id"]?.jsonPrimitive?.content
 
             val geom = json["geometry"]?.jsonObject
-            val geometry: Geometry? = if (geom != null) Geometry.fromJson(geom) else null
+            val geometry: T? = if (geom != null) Geometry.fromJson(geom) as? T else null
 
             return Feature(geometry, json["properties"]?.jsonObject ?: emptyMap(), id, bbox)
         }
diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/FeatureCollection.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/FeatureCollection.kt
index 6fb43fa3..f197b512 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/FeatureCollection.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/FeatureCollection.kt
@@ -23,11 +23,14 @@ import kotlin.jvm.JvmStatic
  */
 @Serializable(with = FeatureCollectionSerializer::class)
 class FeatureCollection(
-    val features: List<Feature> = emptyList(),
+    val features: List<Feature<Geometry>> = emptyList(),
     override val bbox: BoundingBox? = null
-) : Collection<Feature> by features, GeoJson {
+) : Collection<Feature<Geometry>> by features, GeoJson {
 
-    constructor(vararg features: Feature, bbox: BoundingBox? = null) : this(features.toMutableList(), bbox)
+    constructor(vararg features: Feature<Geometry>, bbox: BoundingBox? = null) : this(
+        features.toMutableList(),
+        bbox
+    )
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
@@ -52,7 +55,7 @@ class FeatureCollection(
     override fun json(): String =
         """{"type":"FeatureCollection",${bbox.jsonProp()}"features":${features.jsonJoin { it.json() }}}"""
 
-    operator fun component1(): List<Feature> = features
+    operator fun component1(): List<Feature<*>> = features
     operator fun component2(): BoundingBox? = bbox
 
     companion object {
@@ -74,7 +77,7 @@ class FeatureCollection(
             }
 
             val bbox = json["bbox"]?.jsonArray?.toBbox()
-            val features = json.getValue("features").jsonArray.map { Feature.fromJson(it.jsonObject) }
+            val features = json.getValue("features").jsonArray.map { Feature.fromJson<Geometry>(it.jsonObject) }
 
             return FeatureCollection(features, bbox)
         }
diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/dsl/FeatureCollectionDsl.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/dsl/FeatureCollectionDsl.kt
index 970f0e65..3e286ed2 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/dsl/FeatureCollectionDsl.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/dsl/FeatureCollectionDsl.kt
@@ -10,10 +10,10 @@ import kotlin.jvm.JvmName
 
 @GeoJsonDsl
 class FeatureCollectionDsl(
-    private val features: MutableList<Feature> = mutableListOf(),
+    private val features: MutableList<Feature<Geometry>> = mutableListOf(),
     var bbox: BoundingBox? = null
 ) {
-    operator fun Feature.unaryPlus() {
+    operator fun Feature<Geometry>.unaryPlus() {
         features.add(this)
     }
 
diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializer.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializer.kt
index ed7bb5d9..20508313 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializer.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializer.kt
@@ -2,7 +2,6 @@ package io.github.dellisd.spatialk.geojson.serialization
 
 import io.github.dellisd.spatialk.geojson.FeatureCollection
 import io.github.dellisd.spatialk.geojson.serialization.BoundingBoxSerializer.toJsonArray
-import io.github.dellisd.spatialk.geojson.serialization.FeatureSerializer.toJsonObject
 import kotlinx.serialization.descriptors.SerialDescriptor
 import kotlinx.serialization.descriptors.buildClassSerialDescriptor
 import kotlinx.serialization.json.JsonDecoder
@@ -16,7 +15,7 @@ object FeatureCollectionSerializer : JsonSerializer<FeatureCollection> {
     override val descriptor: SerialDescriptor = buildClassSerialDescriptor("FeatureCollection")
 
     override fun deserialize(input: JsonDecoder): FeatureCollection {
-        return FeatureCollection.Companion.fromJson(input.decodeJsonElement().jsonObject)
+        return FeatureCollection.fromJson(input.decodeJsonElement().jsonObject)
     }
 
     override fun serialize(output: JsonEncoder, value: FeatureCollection) {
@@ -26,7 +25,7 @@ object FeatureCollectionSerializer : JsonSerializer<FeatureCollection> {
             put(
                 "features",
                 buildJsonArray {
-                    value.features.forEach { add(it.toJsonObject()) }
+                    value.features.forEach { feature -> add(feature.toJsonObject()) }
                 }
             )
         }
diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureSerializer.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureSerializer.kt
index 8c3a5ba1..d6cb0ce9 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureSerializer.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureSerializer.kt
@@ -1,6 +1,7 @@
 package io.github.dellisd.spatialk.geojson.serialization
 
 import io.github.dellisd.spatialk.geojson.Feature
+import io.github.dellisd.spatialk.geojson.Geometry
 import io.github.dellisd.spatialk.geojson.serialization.BoundingBoxSerializer.toJsonArray
 import io.github.dellisd.spatialk.geojson.serialization.GeometrySerializer.toJsonObject
 import kotlinx.serialization.descriptors.SerialDescriptor
@@ -12,21 +13,22 @@ import kotlinx.serialization.json.buildJsonObject
 import kotlinx.serialization.json.jsonObject
 import kotlinx.serialization.json.put
 
-object FeatureSerializer : JsonSerializer<Feature> {
+internal class FeatureSerializer<T : Geometry> : JsonSerializer<Feature<T>> {
     override val descriptor: SerialDescriptor = buildClassSerialDescriptor("Feature")
 
-    override fun deserialize(input: JsonDecoder): Feature = Feature.fromJson(input.decodeJsonElement().jsonObject)
+    override fun deserialize(input: JsonDecoder): Feature<T> = Feature.fromJson(input.decodeJsonElement().jsonObject)
 
-    override fun serialize(output: JsonEncoder, value: Feature) {
+    override fun serialize(output: JsonEncoder, value: Feature<T>) {
         output.encodeJsonElement(value.toJsonObject())
     }
 
-    internal fun Feature.toJsonObject() = buildJsonObject {
-        put("type", "Feature")
-        bbox?.let { put("bbox", it.toJsonArray()) }
-        geometry?.let { put("geometry", it.toJsonObject()) }
-        id?.let { put("id", it) }
+}
 
-        put("properties", JsonObject(properties))
-    }
+internal fun <T : Geometry> Feature<T>.toJsonObject() = buildJsonObject {
+    put("type", "Feature")
+    bbox?.let { put("bbox", it.toJsonArray()) }
+    geometry?.let { put("geometry", it.toJsonObject()) }
+    id?.let { put("id", it) }
+
+    put("properties", JsonObject(properties))
 }
diff --git a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/Utils.kt b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/Utils.kt
index 51218f0f..0cde3bc0 100644
--- a/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/Utils.kt
+++ b/geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/serialization/Utils.kt
@@ -4,9 +4,7 @@ import io.github.dellisd.spatialk.geojson.BoundingBox
 import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.Position
 import kotlinx.serialization.json.JsonArray
-import kotlinx.serialization.json.buildJsonArray
 import kotlinx.serialization.json.double
-import kotlinx.serialization.json.jsonArray
 import kotlinx.serialization.json.jsonPrimitive
 
 internal fun DoubleArray.jsonJoin(transform: ((Double) -> CharSequence)? = null) =
@@ -17,7 +15,7 @@ internal fun <T> Iterable<T>.jsonJoin(transform: ((T) -> CharSequence)? = null)
 
 internal fun BoundingBox?.jsonProp(): String = if (this == null) "" else """"bbox":${this.json()},"""
 
-internal fun Feature.idProp(): String = if (this.id == null) "" else """"id":"${this.id}","""
+internal fun Feature<*>.idProp(): String = if (this.id == null) "" else """"id":"${this.id}","""
 
 internal fun JsonArray.toPosition(): Position =
     Position(this[0].jsonPrimitive.double, this[1].jsonPrimitive.double, this.getOrNull(2)?.jsonPrimitive?.double)
diff --git a/geojson/src/commonTest/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializationTests.kt b/geojson/src/commonTest/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializationTests.kt
index a2624ca4..4e47a6bb 100644
--- a/geojson/src/commonTest/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializationTests.kt
+++ b/geojson/src/commonTest/kotlin/io/github/dellisd/spatialk/geojson/serialization/FeatureCollectionSerializationTests.kt
@@ -2,6 +2,7 @@ package io.github.dellisd.spatialk.geojson.serialization
 
 import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.FeatureCollection
+import io.github.dellisd.spatialk.geojson.LineString
 import io.github.dellisd.spatialk.geojson.Position
 import io.github.dellisd.spatialk.geojson.Point
 import kotlinx.serialization.encodeToString
@@ -35,6 +36,30 @@ class FeatureCollectionSerializationTests {
         assertEquals(json, Json.encodeToString(collection), "FeatureCollection (kotlinx)")
     }
 
+    @Test
+    fun testSerializePolymorphicFeatureCollection() {
+        val position = Position(12.3, 45.6)
+        val point = Point(position)
+        val featurePoint = Feature(
+            point, mapOf(
+                "size" to JsonPrimitive(45.1),
+                "name" to JsonPrimitive("Nowhere")
+            )
+        )
+        val line = LineString(coordinates = listOf(position, Position(position.component2(), position.component1())))
+        val featureLine = Feature(line)
+        val collection = FeatureCollection(featurePoint, featureLine)
+        val json =
+            """{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":
+            |[12.3,45.6]},"properties":{"size":45.1,"name":"Nowhere"}},{"type":"Feature","geometry":{"type":
+            |"LineString","coordinates":[[12.3,45.6],[45.6,12.3]]},"properties":{}}]}"""
+                .trimMargin()
+                .replace("\n", "")
+        assertEquals(json, collection.json(), "FeatureCollection (fast)")
+        assertEquals(json, Json.encodeToString(collection), "FeatureCollection (kotlinx)")
+    }
+
+
     @Test
     fun testDeserializeFeatureCollection() {
         val geometry = Point(Position(12.3, 45.6))
@@ -57,4 +82,29 @@ class FeatureCollectionSerializationTests {
             )
         )
     }
+
+    @Test
+    fun testDeerializePolymorphicFeatureCollection() {
+        val position = Position(12.3, 45.6)
+        val point = Point(position)
+        val featurePoint = Feature(
+            point, mapOf(
+                "size" to JsonPrimitive(45.1),
+                "name" to JsonPrimitive("Nowhere")
+            )
+        )
+        val line = LineString(coordinates = listOf(position, Position(position.component2(), position.component1())))
+        val featureLine = Feature(line)
+        val collection = FeatureCollection(featurePoint, featureLine)
+        assertEquals(
+            collection,
+            FeatureCollection.fromJson(
+                """{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":
+                |[12.3,45.6]},"properties":{"size":45.1,"name":"Nowhere"}},{"type":"Feature","geometry":{"type":
+                |"LineString","coordinates":[[12.3,45.6],[45.6,12.3]]},"properties":{}}]}"""
+                    .trimMargin()
+                    .replace("\n", "")
+            )
+        )
+    }
 }
diff --git a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Booleans.kt b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Booleans.kt
index fe1be0eb..4a06555f 100644
--- a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Booleans.kt
+++ b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Booleans.kt
@@ -20,6 +20,7 @@ import kotlin.jvm.JvmOverloads
  * the point is inside the polygon otherwise false.
  * @return `true` if the Position is inside the Polygon; `false` if the Position is not inside the Polygon
  */
+@ExperimentalTurfApi
 @JvmOverloads
 fun booleanPointInPolygon(point: Point, polygon: Polygon, ignoreBoundary: Boolean = false): Boolean {
     val bbox = bbox(polygon)
@@ -38,6 +39,7 @@ fun booleanPointInPolygon(point: Point, polygon: Polygon, ignoreBoundary: Boolea
  * the point is inside the polygon otherwise false.
  * @return `true` if the Position is inside the Polygon; `false` if the Position is not inside the Polygon
  */
+@OptIn(ExperimentalTurfApi::class)
 @JvmOverloads
 fun booleanPointInPolygon(point: Point, polygon: MultiPolygon, ignoreBoundary: Boolean = false): Boolean {
     val bbox = bbox(polygon)
diff --git a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Grids.kt b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Grids.kt
index 328ecfea..1b008cf2 100644
--- a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Grids.kt
+++ b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Grids.kt
@@ -3,6 +3,7 @@ package io.github.dellisd.spatialk.turf
 import io.github.dellisd.spatialk.geojson.BoundingBox
 import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.FeatureCollection
+import io.github.dellisd.spatialk.geojson.Geometry
 import io.github.dellisd.spatialk.geojson.Polygon
 import io.github.dellisd.spatialk.geojson.Position
 import kotlin.math.abs
@@ -24,7 +25,7 @@ fun squareGrid(
     cellHeight: Double,
     units: Units = Units.Kilometers
 ): FeatureCollection {
-    val featureList = mutableListOf<Feature>()
+    val featureList = mutableListOf<Feature<Geometry>>()
     val west = bbox.southwest.longitude
     val south = bbox.southwest.latitude
     val east = bbox.northeast.longitude
@@ -33,8 +34,8 @@ fun squareGrid(
     val bboxWidth = east - west
     val cellWidthDeg = convertLength(cellWidth, units, Units.Degrees)
 
-    val bboxHeight = north - south;
-    val cellHeightDeg = convertLength(cellHeight, units, Units.Degrees);
+    val bboxHeight = north - south
+    val cellHeightDeg = convertLength(cellHeight, units, Units.Degrees)
 
     val columns = floor(abs(bboxWidth) / cellWidthDeg)
     val rows = floor(abs(bboxHeight) / cellHeightDeg)
@@ -43,9 +44,9 @@ fun squareGrid(
     val deltaY = (bboxHeight - rows * cellHeightDeg) / 2
 
     var currentX = west + deltaX
-    repeat (columns.toInt()) {
+    repeat(columns.toInt()) {
         var currentY = south + deltaY
-        repeat (rows.toInt()) {
+        repeat(rows.toInt()) {
             val positions = mutableListOf<Position>().apply {
                 add(Position(currentX, currentY))
                 add(Position(currentX, currentY + cellHeightDeg))
@@ -58,9 +59,9 @@ fun squareGrid(
             }.also {
                 featureList.add(Feature(Polygon(it)))
             }
-            currentY += cellHeightDeg;
+            currentY += cellHeightDeg
         }
-        currentX += cellWidthDeg;
+        currentX += cellWidthDeg
     }
     return FeatureCollection(featureList)
 }
diff --git a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Measurement.kt b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Measurement.kt
index 817099a9..4b3ba9b1 100644
--- a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Measurement.kt
+++ b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Measurement.kt
@@ -44,6 +44,7 @@ fun along(line: LineString, distance: Double, units: Units = Units.Kilometers):
         when {
             distance >= travelled && i == line.coordinates.size - 1 -> {
             }
+
             travelled >= distance -> {
                 val overshot = distance - travelled
                 return if (overshot == 0.0) coordinate
@@ -60,6 +61,7 @@ fun along(line: LineString, distance: Double, units: Units = Units.Kilometers):
                     )
                 }
             }
+
             else -> travelled += distance(
                 coordinate,
                 line.coordinates[i + 1],
@@ -85,6 +87,7 @@ fun area(geometry: Geometry): Double {
                 geom
             )
         }
+
         else -> calculateArea(geometry)
     }
 }
@@ -97,6 +100,7 @@ private fun calculateArea(geometry: Geometry): Double {
                 coords
             )
         }
+
         else -> 0.0
     }
 }
@@ -140,11 +144,13 @@ private fun ringArea(coordinates: List<Position>): Double {
                     middleIndex = coordinates.size - 1
                     upperIndex = 0
                 }
+
                 coordinates.size - 1 -> {
                     lowerIndex = coordinates.size - 1
                     middleIndex = 0
                     upperIndex = 1
                 }
+
                 else -> {
                     lowerIndex = i
                     middleIndex = i + 1
@@ -231,7 +237,7 @@ fun bbox(geometry: MultiPolygon) = computeBbox(geometry.coordAll())
  * @return A [BoundingBox] that covers the geometry.
  */
 @ExperimentalTurfApi
-fun bbox(feature: Feature): BoundingBox = computeBbox(feature.coordAll() ?: emptyList())
+fun bbox(feature: Feature<Geometry>): BoundingBox = computeBbox(feature.coordAll() ?: emptyList())
 
 /**
  * Takes a feature collection and calculates a bbox that covers all features in the collection.
@@ -472,7 +478,7 @@ fun midpoint(point1: Position, point2: Position): Position {
  * @return A [Point] holding the center coordinates
  */
 @ExperimentalTurfApi
-fun center(feature: Feature): Point {
+fun center(feature: Feature<Geometry>): Point {
     val ext = bbox(feature)
     val x = (ext.southwest.longitude + ext.northeast.longitude) / 2
     val y = (ext.southwest.latitude + ext.northeast.latitude) / 2
diff --git a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Meta.kt b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Meta.kt
index 21665c86..b29080c8 100644
--- a/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Meta.kt
+++ b/turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Meta.kt
@@ -52,7 +52,7 @@ fun GeometryCollection.coordAll() =
     geometries.fold(emptyList<Position>()) { acc, geometry -> acc + geometry.coordAll() }
 
 @ExperimentalTurfApi
-fun Feature.coordAll() = geometry?.coordAll()
+fun Feature<Geometry>.coordAll() = geometry?.coordAll()
 
 @ExperimentalTurfApi
 fun FeatureCollection.coordAll() =
diff --git a/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/BooleansTests.kt b/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/BooleansTests.kt
index 5887bfdf..657a5da0 100644
--- a/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/BooleansTests.kt
+++ b/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/BooleansTests.kt
@@ -12,6 +12,7 @@ import kotlin.test.assertEquals
 import kotlin.test.assertFalse
 import kotlin.test.assertTrue
 
+@OptIn(ExperimentalTurfApi::class)
 @ExperimentalSerializationApi
 class BooleansTests {
 
@@ -61,7 +62,7 @@ class BooleansTests {
         val ptInHole = point(-86.69208526611328, 36.20373274711739)
         val ptInPoly = point(-86.72229766845702, 36.20258997094334)
         val ptOutsidePoly = point(-86.75079345703125, 36.18527313913089)
-        val polyHole = Feature.fromJson(readResource("booleans/in/poly-with-hole.geojson")).geometry as Polygon
+        val polyHole = Feature.fromJson<Polygon>(readResource("booleans/in/poly-with-hole.geojson")).geometry as Polygon
 
         assertFalse(booleanPointInPolygon(ptInHole, polyHole))
         assertTrue(booleanPointInPolygon(ptInPoly, polyHole))
@@ -75,7 +76,7 @@ class BooleansTests {
         val ptInPoly2 = point(-86.75079345703125, 36.18527313913089)
         val ptOutsidePoly = point(-86.75302505493164, 36.23015046460186)
         val multiPolyHole =
-            Feature.fromJson(readResource("booleans/in/multipoly-with-hole.geojson")).geometry as MultiPolygon
+            Feature.fromJson<MultiPolygon>(readResource("booleans/in/multipoly-with-hole.geojson")).geometry!!
 
         assertFalse(booleanPointInPolygon(ptInHole, multiPolyHole))
         assertTrue(booleanPointInPolygon(ptInPoly, multiPolyHole))
diff --git a/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/TransformationTest.kt b/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/TransformationTest.kt
index 2843f1e1..1807f453 100644
--- a/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/TransformationTest.kt
+++ b/turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/TransformationTest.kt
@@ -11,18 +11,18 @@ class TransformationTest {
 
     @Test
     fun testBezierSplineIn() {
-        val feature = Feature.fromJson(readResource("transformation/bezierspline/in/bezierIn.json"))
-        val expectedOut = Feature.fromJson(readResource("transformation/bezierspline/out/bezierIn.json"))
+        val feature = Feature.fromJson<LineString>(readResource("transformation/bezierspline/in/bezierIn.json"))
+        val expectedOut = Feature.fromJson<LineString>(readResource("transformation/bezierspline/out/bezierIn.json"))
 
-        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry as LineString))
+        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry!!))
     }
 
     @Test
     fun testBezierSplineSimple() {
-        val feature = Feature.fromJson(readResource("transformation/bezierspline/in/simple.json"))
-        val expectedOut = Feature.fromJson(readResource("transformation/bezierspline/out/simple.json"))
+        val feature = Feature.fromJson<LineString>(readResource("transformation/bezierspline/in/simple.json"))
+        val expectedOut = Feature.fromJson<LineString>(readResource("transformation/bezierspline/out/simple.json"))
 
-        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry as LineString))
+        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry!!))
     }
 
     /**
@@ -32,9 +32,9 @@ class TransformationTest {
      */
     @Test
     fun testBezierSplineAcrossPacific() {
-        val feature = Feature.fromJson(readResource("transformation/bezierspline/in/issue-#1063.json"))
-        val expectedOut = Feature.fromJson(readResource("transformation/bezierspline/out/issue-#1063.json"))
+        val feature = Feature.fromJson<LineString>(readResource("transformation/bezierspline/in/issue-#1063.json"))
+        val expectedOut = Feature.fromJson<LineString>(readResource("transformation/bezierspline/out/issue-#1063.json"))
 
-        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry as LineString))
+        assertEquals(expectedOut.geometry, bezierSpline(feature.geometry!!))
     }
 }