diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93d9039b50e..5aafe3ce59f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@
   [@nagelflorian](https://github.com/nagelflorian) in [#936](https://github.com/apollographql/graphql-tools/pull/936)
 * Update `IFieldResolver` to allow typed input args.  <br/>
   [@luk3thomas](https://github.com/luk3thomas) in [#932](https://github.com/apollographql/graphql-tools/pull/932)
+* Changes to `extractExtensionDefinitions` to properly support `graphql-js` input extensions.  <br/>
+  [@jure](https://github.com/jure) in [#948](https://github.com/apollographql/graphql-tools/pull/948)
 * Documentation updates.  <br/>
   [@Amorites](https://github.com/Amorites) in [#944](https://github.com/apollographql/graphql-tools/pull/944)  <br/>
   [@trevor-scheer](https://github.com/trevor-scheer) in [#946](https://github.com/apollographql/graphql-tools/pull/946)  <br/>
diff --git a/src/generate/extractExtensionDefinitions.ts b/src/generate/extractExtensionDefinitions.ts
index 05fb394411c..54d8dd671e6 100644
--- a/src/generate/extractExtensionDefinitions.ts
+++ b/src/generate/extractExtensionDefinitions.ts
@@ -2,12 +2,14 @@ import { DocumentNode, DefinitionNode } from 'graphql';
 
 const newExtensionDefinitionKind = 'ObjectTypeExtension';
 const interfaceExtensionDefinitionKind = 'InterfaceTypeExtension';
+const inputObjectExtensionDefinitionKind = 'InputObjectTypeExtension';
 
 export default function extractExtensionDefinitions(ast: DocumentNode) {
   const extensionDefs = ast.definitions.filter(
     (def: DefinitionNode) =>
       (def.kind as any) === newExtensionDefinitionKind ||
-      (def.kind as any) === interfaceExtensionDefinitionKind,
+      (def.kind as any) === interfaceExtensionDefinitionKind ||
+      (def.kind as any) === inputObjectExtensionDefinitionKind,
   );
 
   return Object.assign({}, ast, {
diff --git a/src/test/testExtensionExtraction.ts b/src/test/testExtensionExtraction.ts
new file mode 100644
index 00000000000..a5ab306c458
--- /dev/null
+++ b/src/test/testExtensionExtraction.ts
@@ -0,0 +1,25 @@
+import { expect } from 'chai';
+import { parse } from 'graphql';
+import extractExtensionDefinitons from '../generate/extractExtensionDefinitions';
+import 'mocha';
+
+describe('Extension extraction', () => {
+  it('extracts extended inputs', () => {
+    const typeDefs = `
+      input Input {
+        foo: String
+      }
+
+      extend input Input {
+        bar: String
+      }
+    `;
+
+    const astDocument = parse(typeDefs);
+    const extensionAst = extractExtensionDefinitons(astDocument);
+
+    expect(extensionAst.definitions).to.have.length(1);
+    expect(extensionAst.definitions[0].kind).to.equal('InputObjectTypeExtension');
+  });
+});
+
diff --git a/src/test/tests.ts b/src/test/tests.ts
index edc4fabca67..7da887e0719 100755
--- a/src/test/tests.ts
+++ b/src/test/tests.ts
@@ -12,3 +12,4 @@ import './testMocking';
 import './testResolution';
 import './testSchemaGenerator';
 import './testTransforms';
+import './testExtensionExtraction';