diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -2631,6 +2631,7 @@
   DSAStack->pop();
   DiscardCleanupsInEvaluationContext();
   PopExpressionEvaluationContext();
+  CleanupVarDeclMarking();
 }
 
 static bool FinishOpenMPLinearClause(OMPLinearClause &Clause, DeclRefExpr *IV,
diff --git a/clang/test/OpenMP/sema_alignas.cpp b/clang/test/OpenMP/sema_alignas.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/OpenMP/sema_alignas.cpp
@@ -0,0 +1,86 @@
+// RUN: %clang_cc1 -verify=expected,omp45 -fopenmp -fopenmp-version=45 %s
+// RUN: %clang_cc1 -verify=expected,omp50 -fopenmp -fopenmp-version=50 %s
+
+// RUN: %clang_cc1 -verify=expected,omp45 -fopenmp-simd -fopenmp-version=45 %s
+// RUN: %clang_cc1 -verify=expected,omp50 -fopenmp-simd -fopenmp-version=50 %s
+
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+struct FOO {
+  static const int vec_align_bytes = 32;
+
+  void foo() {
+    alignas(vec_align_bytes) double a;
+#pragma omp parallel
+    a++;
+
+#pragma omp master
+    a++;
+
+#pragma omp parallel private(a)
+    a++;
+  }
+};
+
+namespace {
+class FOO {
+public:
+  static const int vec_align_bytes = 32;
+
+  void foo() {
+    alignas(vec_align_bytes) double a;
+#pragma omp parallel
+    a++;
+
+#pragma omp master
+    a++;
+
+#pragma omp parallel private(a)
+    a++;
+  }
+};
+} // namespace
+
+template <typename T>
+struct FOO : public T {
+  static const T vec_align_bytes = 32;
+
+  void foo() {
+    alignas(vec_align_bytes) double a;
+#pragma omp parallel
+    a++;
+
+#pragma omp master
+    a++;
+
+#pragma omp parallel private(a)
+    a++;
+  }
+};
+
+namespace {
+namespace {
+template <typename T>
+class FOO : public T {
+public:
+  static const T vec_align_bytes = 32;
+
+  void foo() {
+    alignas(vec_align_bytes) double a;
+#pragma omp parallel
+    a++;
+
+#pragma omp master
+    a++;
+
+#pragma omp parallel private(a)
+    a++;
+  }
+};
+} // namespace
+} // namespace
+
+#endif