diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5142,8 +5142,11 @@
   case Stmt::ReturnStmtClass: {
     const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
     FullExpressionRAII Scope(Info);
-    if (RetExpr && RetExpr->isValueDependent())
-      return EvaluateDependentExpr(RetExpr, Info) ? ESR_Returned : ESR_Failed;
+    if (RetExpr && RetExpr->isValueDependent()) {
+      EvaluateDependentExpr(RetExpr, Info);
+      // We know we returned, but we don't know what the value is.
+      return ESR_Failed;
+    }
     if (RetExpr &&
         !(Result.Slot
               ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
diff --git a/clang/test/SemaCXX/constexpr-function-recovery-crash.cpp b/clang/test/SemaCXX/constexpr-function-recovery-crash.cpp
--- a/clang/test/SemaCXX/constexpr-function-recovery-crash.cpp
+++ b/clang/test/SemaCXX/constexpr-function-recovery-crash.cpp
@@ -66,3 +66,6 @@
 constexpr int test9(int x) {
   return f<1>(f<x>(1)); // expected-error {{no matching function for call to 'f'}}
 }
+
+constexpr int test10() { return undef(); } // expected-error {{use of undeclared identifier 'undef'}}
+static_assert(test10() <= 1, "should not crash"); // expected-error {{static_assert expression is not an integral constant expression}}