diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f550fcf9c35..43311c81f7b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15138,7 +15138,7 @@ namespace ts {
                     }
                 }
                 // Return a union of the return expression types.
-                type = getUnionType(yieldTypes ? yieldTypes.concat(types) : types, /*subtypeReduction*/ true);
+                type = getUnionType(types, /*subtypeReduction*/ true);
 
                 if (functionFlags & FunctionFlags.Generator) { // AsyncGenerator function or Generator function
                     type = functionFlags & FunctionFlags.Async