diff --git a/backend/src/main/scala/cromwell/backend/validation/RuntimeAttributesValidation.scala b/backend/src/main/scala/cromwell/backend/validation/RuntimeAttributesValidation.scala
index 5fa52dac53a..a5febfd88e2 100644
--- a/backend/src/main/scala/cromwell/backend/validation/RuntimeAttributesValidation.scala
+++ b/backend/src/main/scala/cromwell/backend/validation/RuntimeAttributesValidation.scala
@@ -84,6 +84,8 @@ object RuntimeAttributesValidation {
       override protected def validateValue: PartialFunction[WomValue, ErrorOr[ValidatedType]] =
         validation.validateValuePackagePrivate
 
+      override protected def validateNone: ErrorOr[ValidatedType] = validateValue(default)
+
       override protected def validateExpression: PartialFunction[WomValue, Boolean] =
         validation.validateExpressionPackagePrivate
 
@@ -108,6 +110,8 @@ object RuntimeAttributesValidation {
       override protected def validateValue: PartialFunction[WomValue, ErrorOr[ValidatedType]] =
         validation.validateValuePackagePrivate
 
+      override protected def validateNone: ErrorOr[ValidatedType] = validation.validateNone
+
       override protected def validateExpression: PartialFunction[WomValue, Boolean] =
         validation.validateExpressionPackagePrivate
 
@@ -482,5 +486,9 @@ trait OptionalRuntimeAttributesValidation[ValidatedType] extends RuntimeAttribut
       validateOption.apply(womValue).map(Option.apply)
   }
 
-  final override protected lazy val validateNone: ErrorOr[None.type] = None.validNel[String]
+  final override protected lazy val validateNone: ErrorOr[Option[ValidatedType]] =
+    staticDefaultOption match {
+      case Some(default) => validateValue(default)
+      case None => None.validNel[String]
+    }
 }
diff --git a/supportedBackends/sfs/src/test/scala/cromwell/backend/impl/sfs/config/ConfigInitializationActorSpec.scala b/supportedBackends/sfs/src/test/scala/cromwell/backend/impl/sfs/config/ConfigInitializationActorSpec.scala
index 085ac5cd974..a86cf3cc7ef 100644
--- a/supportedBackends/sfs/src/test/scala/cromwell/backend/impl/sfs/config/ConfigInitializationActorSpec.scala
+++ b/supportedBackends/sfs/src/test/scala/cromwell/backend/impl/sfs/config/ConfigInitializationActorSpec.scala
@@ -4,8 +4,18 @@ import com.typesafe.config.ConfigFactory
 import common.assertion.CromwellTimeoutSpec
 import org.scalatest.flatspec.AnyFlatSpec
 import org.scalatest.matchers.should.Matchers
+import org.scalatest.prop.{TableDrivenPropertyChecks, TableFor4}
+import wdl4s.parser.MemoryUnit
+import wom.format.MemorySize
+import wom.values.{WomString, WomValue}
+import cats.syntax.validated._
+import common.validation.ErrorOr._
 
-class ConfigInitializationActorSpec extends AnyFlatSpec with CromwellTimeoutSpec with Matchers {
+class ConfigInitializationActorSpec
+    extends AnyFlatSpec
+    with CromwellTimeoutSpec
+    with Matchers
+    with TableDrivenPropertyChecks {
 
   it should "read the list of call cache attributes from config" in {
     val tripleQuote = "\"\"\""
@@ -45,4 +55,64 @@ class ConfigInitializationActorSpec extends AnyFlatSpec with CromwellTimeoutSpec
 
   }
 
+  private val attributeValidationTests: TableFor4[String, String, Map[String, WomValue], ErrorOr[_]] = Table(
+    ("description", "declaration", "womValue", "expected"),
+    ("present required custom", "Int my_attr", Map("my_attr" -> WomString("1")), 1.valid),
+    ("missing required custom",
+     "Int my_attr",
+     Map(),
+     "Expecting my_attr runtime attribute to be an Integer".invalidNel
+    ),
+    ("present defaulted custom", "Int my_attr = 415", Map("my_attr" -> WomString("1")), 1.valid),
+    ("missing defaulted custom", "Int my_attr = 415", Map(), 415.valid),
+    ("present optional custom", "Int? my_attr", Map("my_attr" -> WomString("1")), Option(1).valid),
+    ("missing optional custom", "Int? my_attr", Map(), None.valid),
+    ("present defaulted optional custom", "Int? my_attr = 415", Map("my_attr" -> WomString("1")), Option(1).valid),
+    ("missing defaulted optional custom", "Int? my_attr = 415", Map(), Option(415).valid),
+    ("present required memory",
+     "Float memory_gb",
+     Map("memory" -> WomString("3 GB")),
+     MemorySize(3, MemoryUnit.GB).valid
+    ),
+    ("missing required memory",
+     "Float memory_gb",
+     Map(),
+     "Expecting memory runtime attribute to be an Integer or String with format '8 GB'. Exception: Not supported WDL type value".invalidNel
+    ),
+    ("present defaulted memory",
+     "Float memory_gb = 1",
+     Map("memory" -> WomString("3 GB")),
+     MemorySize(3, MemoryUnit.GB).valid
+    ),
+    ("missing defaulted memory", "Float memory_gb = 1", Map(), MemorySize(1, MemoryUnit.GB).valid),
+    ("present optional memory",
+     "Float? memory_gb",
+     Map("memory" -> WomString("3 GB")),
+     Option(MemorySize(3, MemoryUnit.GB)).valid
+    ),
+    ("missing optional memory", "Float? memory_gb", Map(), None.valid),
+    ("present defaulted optional memory",
+     "Float? memory_gb = 1",
+     Map("memory" -> WomString("3 GB")),
+     Option(MemorySize(3, MemoryUnit.GB)).valid
+    ),
+    ("missing defaulted optional memory", "Float? memory_gb = 1", Map(), Option(MemorySize(1, MemoryUnit.GB)).valid)
+  )
+  forAll(attributeValidationTests) { (description, declaration, values, expected) =>
+    it should s"validate a $description attribute" in {
+      val backendConfig = ConfigFactory.parseString(
+        s"""submit: "unused"
+           |runtime-attributes: "$declaration"
+           |""".stripMargin
+      )
+      lazy val configWdlNamespace = new ConfigWdlNamespace(backendConfig)
+      val validations = DeclarationValidation.fromDeclarations(
+        configWdlNamespace.runtimeDeclarations,
+        configWdlNamespace.callCachedRuntimeAttributes
+      )
+      val validation = validations.head.makeValidation()
+      val actual = validation.validate(values)
+      actual should be(expected)
+    }
+  }
 }