diff --git a/lib/SILOptimizer/Differentiation/Thunk.cpp b/lib/SILOptimizer/Differentiation/Thunk.cpp
index 52b505681ed43..487bce2929183 100644
--- a/lib/SILOptimizer/Differentiation/Thunk.cpp
+++ b/lib/SILOptimizer/Differentiation/Thunk.cpp
@@ -786,10 +786,8 @@ getOrCreateSubsetParametersThunkForDerivativeFunction(
   // Extract all direct results.
   SmallVector<SILValue, 8> directResults;
   extractAllElements(apply, builder, directResults);
-  auto originalDirectResults = ArrayRef<SILValue>(directResults).drop_back(1);
-  auto originalDirectResult =
-      joinElements(originalDirectResults, builder, apply->getLoc());
   auto linearMap = directResults.back();
+  directResults.pop_back();
 
   auto linearMapType = linearMap->getType().castTo<SILFunctionType>();
   auto linearMapTargetType = targetType->getResults()
@@ -830,8 +828,8 @@ getOrCreateSubsetParametersThunkForDerivativeFunction(
          0);
   if (origFnType->getNumResults() > 0 &&
       origFnType->getResults().front().isFormalDirect()) {
-    auto result =
-        joinElements({originalDirectResult, thunkedLinearMap}, builder, loc);
+    directResults.push_back(thunkedLinearMap);
+    auto result = joinElements(directResults, builder, loc);
     builder.createReturn(loc, result);
   } else {
     builder.createReturn(loc, thunkedLinearMap);
diff --git a/test/AutoDiff/SILOptimizer/param_thunk_tuple.swift b/test/AutoDiff/SILOptimizer/param_thunk_tuple.swift
new file mode 100644
index 0000000000000..8a0402a099989
--- /dev/null
+++ b/test/AutoDiff/SILOptimizer/param_thunk_tuple.swift
@@ -0,0 +1,33 @@
+// RUN: %target-swift-frontend -emit-sil %s | %FileCheck %s
+
+// Verify the result type of a subset parameters thunk matches the declaration:
+//
+// CHECK: // autodiff subset parameters thunk for forward-mode derivative from f(x:)
+// CHECK-NEXT: sil shared [transparent] [thunk] @$s17param_thunk_tuple{{.*}} : $@convention(thin) (X)
+// CHECK-SAME: -> (Float, Double, @owned @callee_guaranteed (X.TangentVector) -> Float)
+// CHECK: return
+// CHECK-SAME: %{{.*}} : $(Float, Double, @callee_guaranteed (X.TangentVector) -> Float)
+//
+// CHECK: // autodiff subset parameters thunk for reverse-mode derivative from f(x:)
+// CHECK-NEXT: sil shared [transparent] [thunk] @$s17param_thunk_tuple{{.*}} : $@convention(thin) (X)
+// CHECK-SAME: -> (Float, Double, @owned @callee_guaranteed (Float) -> X.TangentVector)
+// CHECK: return
+// CHECK-SAME: %{{.*}} : $(Float, Double, @callee_guaranteed (Float) -> X.TangentVector)
+
+import _Differentiation
+
+struct X: Differentiable {
+    var a: Float
+    var b: Double
+}
+
+@differentiable(reverse)
+func f(x: X) -> (Float, Double) {
+    (x.a, x.b)
+}
+
+@differentiable(reverse)
+func g1(x: X) -> Float {
+    f(x: x).0
+}
+