diff --git a/src/services/services.ts b/src/services/services.ts
index 0c7b5d97d26..f122e39bcc6 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -412,7 +412,7 @@ namespace ts {
         getDeclaration(): SignatureDeclaration {
             return this.declaration;
         }
-        getTypeParameters(): Type[] {
+        getTypeParameters(): TypeParameter[] {
             return this.typeParameters;
         }
         getParameters(): Symbol[] {
diff --git a/src/services/types.ts b/src/services/types.ts
index a577fb20aac..9253153c004 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -39,7 +39,7 @@ namespace ts {
 
     export interface Signature {
         getDeclaration(): SignatureDeclaration;
-        getTypeParameters(): Type[];
+        getTypeParameters(): TypeParameter[];
         getParameters(): Symbol[];
         getReturnType(): Type;
         getDocumentationComment(): SymbolDisplayPart[];