diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -7927,7 +7927,7 @@
         BO->getRHS()->getType()->isDependentType()) {
       if (BO->getOpcode() != BO_Assign)
         return;
-    } else if (!BO->isAssignmentOp())
+    } else if (!BO->isAssignmentOp() || BO->isCompoundAssignmentOp())
       return;
     LHS = dyn_cast<DeclRefExpr>(BO->getLHS());
   } else if (CXXOperatorCallExpr *COCE = dyn_cast<CXXOperatorCallExpr>(E)) {
diff --git a/clang/test/Sema/warn-unused-but-set-variables.c b/clang/test/Sema/warn-unused-but-set-variables.c
--- a/clang/test/Sema/warn-unused-but-set-variables.c
+++ b/clang/test/Sema/warn-unused-but-set-variables.c
@@ -59,3 +59,10 @@
   __attribute__((__cleanup__(for_cleanup))) int x;
   x = 5;
 }
+
+void f4() {
+  int j = 0;
+  for (int i = 0; i < 1000; i++)
+    j += 1;
+  return;
+}