diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 473c6f7950ae..e34b820625c2 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -120,11 +120,27 @@ public:
 class OMPLoopScope : public CodeGenFunction::RunCleanupsScope {
   void emitPreInitStmt(CodeGenFunction &CGF, const OMPLoopDirective &S) {
     CodeGenFunction::OMPMapVars PreCondVars;
+    llvm::DenseSet<const VarDecl *> EmittedAsPrivate;
     for (const auto *E : S.counters()) {
       const auto *VD = cast<VarDecl>(cast<DeclRefExpr>(E)->getDecl());
+      EmittedAsPrivate.insert(VD->getCanonicalDecl());
       (void)PreCondVars.setVarAddr(
           CGF, VD, CGF.CreateMemTemp(VD->getType().getNonReferenceType()));
     }
+    // Mark private vars as undefs.
+    for (const auto *C : S.getClausesOfKind<OMPPrivateClause>()) {
+      for (const Expr *IRef : C->varlists()) {
+        const auto *OrigVD = cast<VarDecl>(cast<DeclRefExpr>(IRef)->getDecl());
+        if (EmittedAsPrivate.insert(OrigVD->getCanonicalDecl()).second) {
+          (void)PreCondVars.setVarAddr(
+              CGF, OrigVD,
+              Address(llvm::UndefValue::get(
+                          CGF.ConvertTypeForMem(CGF.getContext().getPointerType(
+                              OrigVD->getType().getNonReferenceType()))),
+                      CGF.getContext().getDeclAlign(OrigVD)));
+        }
+      }
+    }
     (void)PreCondVars.apply(CGF);
     if (const auto *PreInits = cast_or_null<DeclStmt>(S.getPreInits())) {
       for (const auto *I : PreInits->decls())
diff --git a/clang/test/OpenMP/parallel_for_codegen.cpp b/clang/test/OpenMP/parallel_for_codegen.cpp
index 4329dd4f9398..9e3390214d78 100644
--- a/clang/test/OpenMP/parallel_for_codegen.cpp
+++ b/clang/test/OpenMP/parallel_for_codegen.cpp
@@ -35,12 +35,14 @@ void with_var_schedule() {
 // CHECK: [[CHUNK:%.+]] = load i64, i64* %
 // CHECK: call void {{.+}} @__kmpc_fork_call({{.+}}, i64 [[CHUNK]])
 
+// CHECK: [[UNDEF_A:%.+]] = load double, double* undef
+// CHECK: fadd double 2.000000e+00, [[UNDEF_A]]
 // CHECK: [[CHUNK_VAL:%.+]] = load i8, i8* %
 // CHECK: [[CHUNK_SIZE:%.+]] = sext i8 [[CHUNK_VAL]] to i64
 // CHECK: call void @__kmpc_for_static_init_8u([[IDENT_T_TY]]* [[LOOP_LOC]], i32 [[GTID:%[^,]+]], i32 33, i32* [[IS_LAST:%[^,]+]], i64* [[OMP_LB:%[^,]+]], i64* [[OMP_UB:%[^,]+]], i64* [[OMP_ST:%[^,]+]], i64 1, i64 [[CHUNK_SIZE]])
 // CHECK: call void @__kmpc_for_static_fini([[IDENT_T_TY]]* [[LOOP_LOC]], i32 [[GTID]])
-#pragma omp parallel for schedule(static, char(a))
-  for (unsigned long long i = 1; i < 2; ++i) {
+#pragma omp parallel for schedule(static, char(a)) private(a)
+  for (unsigned long long i = 1; i < 2 + a; ++i) {
   }
 }