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
@@ -15120,6 +15120,17 @@
           continue;
         }
       }
+    } else {
+      // Threadprivates cannot be shared between threads, so dignose if the base
+      // is a threadprivate variable.
+      DSAStackTy::DSAVarData DVar = Stack->getTopDSA(D, /*FromParent=*/false);
+      if (DVar.CKind == OMPC_threadprivate) {
+        S.Diag(ELoc, diag::err_omp_wrong_dsa)
+            << getOpenMPClauseName(DVar.CKind)
+            << getOpenMPClauseName(OMPC_reduction);
+        reportOriginalDsa(S, Stack, D, DVar);
+        continue;
+      }
     }
 
     // Try to find 'declare reduction' corresponding construct before using
diff --git a/clang/test/OpenMP/parallel_reduction_messages.cpp b/clang/test/OpenMP/parallel_reduction_messages.cpp
--- a/clang/test/OpenMP/parallel_reduction_messages.cpp
+++ b/clang/test/OpenMP/parallel_reduction_messages.cpp
@@ -92,6 +92,8 @@
 
 S3 h, k;
 #pragma omp threadprivate(h) // expected-note 2 {{defined as threadprivate or thread local}}
+int *gptr;
+#pragma omp threadprivate(gptr) // expected-note {{defined as threadprivate or thread local}}
 
 template <class T>       // expected-note {{declared here}}
 T tmain(T argc) {
@@ -277,6 +279,8 @@
   m++;
 #pragma omp parallel reduction(task, + : m) // omp45-error 2 {{expected expression}} omp45-warning {{missing ':' after reduction identifier - ignoring}}
   m++;
+#pragma omp parallel reduction(+:gptr[:argc]) // expected-error {{threadprivate or thread local variable cannot be reduction}}
+  ;
 
   return tmain(argc) + tmain(fl); // expected-note {{in instantiation of function template specialization 'tmain<int>' requested here}} expected-note {{in instantiation of function template specialization 'tmain<float>' requested here}}
 }