diff --git a/lib/Differentiator/ReverseModeVisitor.cpp b/lib/Differentiator/ReverseModeVisitor.cpp
index 5909ca6e4..9ecf043c8 100644
--- a/lib/Differentiator/ReverseModeVisitor.cpp
+++ b/lib/Differentiator/ReverseModeVisitor.cpp
@@ -3314,8 +3314,11 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
     auto* field = ME->getMemberDecl();
     assert(!isa<CXXMethodDecl>(field) &&
            "CXXMethodDecl nodes not supported yet!");
-    MemberExpr* clonedME = utils::BuildMemberExpr(
-        m_Sema, getCurrentScope(), baseDiff.getExpr(), field->getName());
+    Expr* clonedME = baseDiff.getExpr();
+    llvm::StringRef fieldName = field->getName();
+    if (baseDiff.getExpr() && !fieldName.empty())
+      clonedME = utils::BuildMemberExpr(m_Sema, getCurrentScope(),
+                                        baseDiff.getExpr(), fieldName);
     if (clad::utils::hasNonDifferentiableAttribute(ME)) {
       auto* zero = ConstantFolder::synthesizeLiteral(m_Context.IntTy, m_Context,
                                                      /*val=*/0);
@@ -3323,8 +3326,10 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
     }
     if (!baseDiff.getExpr_dx())
       return {clonedME, nullptr};
-    MemberExpr* derivedME = utils::BuildMemberExpr(
-        m_Sema, getCurrentScope(), baseDiff.getExpr_dx(), field->getName());
+    Expr* derivedME = baseDiff.getExpr_dx();
+    if (!fieldName.empty())
+      derivedME = utils::BuildMemberExpr(m_Sema, getCurrentScope(),
+                                         baseDiff.getExpr_dx(), fieldName);
     if (dfdx()) {
       Expr* addAssign =
           BuildOp(BinaryOperatorKind::BO_AddAssign, derivedME, dfdx());
diff --git a/test/Gradient/UserDefinedTypes.C b/test/Gradient/UserDefinedTypes.C
index 6bc61395a..344f185cb 100644
--- a/test/Gradient/UserDefinedTypes.C
+++ b/test/Gradient/UserDefinedTypes.C
@@ -404,6 +404,69 @@ MyStruct fn12(MyStruct s) {
 // CHECK-NEXT:    }
 // CHECK-NEXT:}
 
+typedef int Fint;
+typedef union Findex
+{
+    struct
+    {
+        Fint j, k, l;
+    };
+    Fint dim[3];
+} Findex;
+
+void fn13(double *x, double *y, int size)
+{
+    Findex p;
+
+    for (p.j = 0; p.j < size; p.j += 1)
+    {
+        y[p.j] = 2.0 * x[p.j];
+    }
+}
+
+// CHECK: void fn13_grad_0_1(double *x, double *y, int size, double *_d_x, double *_d_y) {
+// CHECK-NEXT: int _d_size = 0;
+// CHECK-NEXT: Fint _t1;
+// CHECK-NEXT: clad::tape<Fint> _t2 = {};
+// CHECK-NEXT: clad::tape<double> _t3 = {};
+// CHECK-NEXT: Findex _d_p({});
+// CHECK-NEXT: Findex p;
+// CHECK-NEXT: unsigned {{int|long|long long}} _t0 = {{0U|0UL|0ULL}};
+// CHECK-NEXT: _t1 = p.j;
+// CHECK-NEXT: for (p.j = 0; ; clad::push(_t2, p.j) , (p.j += 1)) {
+// CHECK-NEXT:     {
+// CHECK-NEXT:         if (!(p.j < size))
+// CHECK-NEXT:             break;
+// CHECK-NEXT:     }
+// CHECK-NEXT:     _t0++;
+// CHECK-NEXT:     clad::push(_t3, y[p.j]);
+// CHECK-NEXT:     y[p.j] = 2. * x[p.j];
+// CHECK-NEXT: }
+// CHECK-NEXT: {
+// CHECK-NEXT:     for (;; _t0--) {
+// CHECK-NEXT:        {
+// CHECK-NEXT:             if (!_t0)
+// CHECK-NEXT:                 break;
+// CHECK-NEXT:         }
+// CHECK-NEXT:         {
+// CHECK-NEXT:             p.j = clad::pop(_t2);
+// CHECK-NEXT:             Fint _r_d1 = _d_p.j;
+// CHECK-NEXT:         }
+// CHECK-NEXT:         {
+// CHECK-NEXT:             y[p.j] = clad::pop(_t3);
+// CHECK-NEXT:             double _r_d2 = _d_y[p.j];
+// CHECK-NEXT:             _d_y[p.j] = 0.;
+// CHECK-NEXT:             _d_x[p.j] += 2. * _r_d2;
+// CHECK-NEXT:         }
+// CHECK-NEXT:     }
+// CHECK-NEXT:     {
+// CHECK-NEXT:         p.j = _t1;
+// CHECK-NEXT:         Fint _r_d0 = _d_p.j;
+// CHECK-NEXT:        _d_p.j = 0;
+// CHECK-NEXT:     }
+// CHECK-NEXT: }
+// CHECK-NEXT:}
+
 void print(const Tangent& t) {
   for (int i = 0; i < 5; ++i) {
     printf("%.2f", t.data[i]);
@@ -416,6 +479,16 @@ void print(const MyStruct& s) {
   printf("{%.2f, %.2f}\n", s.a, s.b);
 }
 
+void printArray(double* arr, int size) {
+  printf("{");
+  for (int i = 0; i < size; ++i) {
+    printf("%.2f", arr[i]);
+    if (i != size - 1)
+      printf(", ");
+  }
+  printf("}\n");
+}
+
 int main() {
     pairdd p(3, 5), d_p;
     double i = 3, d_i, d_j;
@@ -454,6 +527,14 @@ int main() {
     auto fn12_test = clad::gradient(fn12);
     fn12_test.execute(s, &d_s);
     print(d_s); // CHECK-EXEC: {2.00, 2.00}
+
+    auto fn13_test = clad::gradient(fn13, "x, y");
+    double x[3] = {1.0, 2.0, 3.0}, y[3] = {0.0, 0.0, 0.0};
+    double d_x[3] = {0.0, 0.0, 0.0}, d_y[3] = {1.0, 1.0, 1.0};
+    int size = 3;
+    fn13_test.execute(x, y, 3, d_x, d_y);
+    printArray(d_x, size); // CHECK-EXEC: {2.00, 2.00, 2.00}
+    printArray(d_y, size); // CHECK-EXEC: {0.00, 0.00, 0.00}
 }
 
 // CHECK: void sum_pullback(Tangent &t, double _d_y, Tangent *_d_t) {