diff --git a/apistar/schemas/jsonschema.py b/apistar/schemas/jsonschema.py
index d649f2cc..9d62eb17 100644
--- a/apistar/schemas/jsonschema.py
+++ b/apistar/schemas/jsonschema.py
@@ -1,6 +1,6 @@
 import typesystem
 
-definitions = typesystem.SchemaDefinitions()
+definitions = typesystem.Definitions()
 
 JSON_SCHEMA = (
     typesystem.Object(
diff --git a/apistar/schemas/openapi.py b/apistar/schemas/openapi.py
index b8742699..a894c77b 100644
--- a/apistar/schemas/openapi.py
+++ b/apistar/schemas/openapi.py
@@ -15,7 +15,7 @@
     properties={"$ref": typesystem.String(pattern="^#/components/responses/")}
 )
 
-definitions = typesystem.SchemaDefinitions()
+definitions = typesystem.Definitions()
 
 OPEN_API = typesystem.Object(
     title="OpenAPI",
@@ -367,7 +367,7 @@ def load(self, data):
         )
 
     def get_schema_definitions(self, data):
-        definitions = typesystem.SchemaDefinitions()
+        definitions = typesystem.Definitions()
         schemas = lookup(data, ["components", "schemas"], {})
         for key, value in schemas.items():
             ref = f"#/components/schemas/{key}"
diff --git a/apistar/schemas/swagger.py b/apistar/schemas/swagger.py
index b8bd10ab..74c21daf 100644
--- a/apistar/schemas/swagger.py
+++ b/apistar/schemas/swagger.py
@@ -12,7 +12,7 @@
     properties={"$ref": typesystem.String(pattern="^#/responses/")}
 )
 
-definitions = typesystem.SchemaDefinitions()
+definitions = typesystem.Definitions()
 
 SWAGGER = typesystem.Object(
     title="Swagger",
@@ -357,7 +357,7 @@ def load(self, data):
         )
 
     def get_schema_definitions(self, data):
-        definitions = typesystem.SchemaDefinitions()
+        definitions = typesystem.Definitions()
         schemas = lookup(data, ["components", "schemas"], {})
         for key, value in schemas.items():
             ref = f"#/components/schemas/{key}"
diff --git a/requirements.txt b/requirements.txt
index cf3a4712..56fb385a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ click
 jinja2
 requests
 pyyaml
-typesystem>=0.2.0
+typesystem>=0.3.0,<0.4.0
 
 # Testing requirements
 black
diff --git a/setup.py b/setup.py
index 282b8136..71bdbe16 100755
--- a/setup.py
+++ b/setup.py
@@ -69,7 +69,7 @@ def get_long_description(long_description_file):
     author_email="tom@tomchristie.com",
     packages=get_packages("apistar"),
     package_data=get_package_data("apistar"),
-    install_requires=["click", "jinja2", "requests", "pyyaml", "typesystem"],
+    install_requires=["click", "jinja2", "requests", "pyyaml", "typesystem~=0.3"],
     python_requires=">=3.6",
     classifiers=[
         "Development Status :: 3 - Alpha",