diff --git a/clang/lib/AST/Interp/ByteCodeExprGen.cpp b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
index 27e0986192165c..7f97d8ce9fb804 100644
--- a/clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -2510,6 +2510,12 @@ template <class Emitter>
 bool ByteCodeExprGen<Emitter>::visitDecl(const VarDecl *VD) {
   assert(!VD->isInvalidDecl() && "Trying to constant evaluate an invalid decl");
 
+  // Global variable we've already seen but that's uninitialized means
+  // evaluating the initializer failed. Just return failure.
+  if (std::optional<unsigned> Index = P.getGlobal(VD);
+      Index && !P.getPtrGlobal(*Index).isInitialized())
+    return false;
+
   // Create and initialize the variable.
   if (!this->visitVarDecl(VD))
     return false;
diff --git a/clang/test/SemaCXX/PR20334-std_initializer_list_diagnosis_assertion.cpp b/clang/test/SemaCXX/PR20334-std_initializer_list_diagnosis_assertion.cpp
index ec672089b84aaa..fb1feee01b29f1 100644
--- a/clang/test/SemaCXX/PR20334-std_initializer_list_diagnosis_assertion.cpp
+++ b/clang/test/SemaCXX/PR20334-std_initializer_list_diagnosis_assertion.cpp
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 -std=c++11 -verify -emit-llvm-only %s
 // RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify %s -DCPP98
+// RUN: %clang_cc1 -std=c++11 -verify -emit-llvm-only %s -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify %s -DCPP98 -fexperimental-new-constant-interpreter
+
 
 namespace std {
   template <class _E>