diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3327,9 +3327,11 @@
   }
 
   if (HasDeducedReturnType) {
+    FunctionDecl *FD = CurLambda->CallOperator;
+    if (FD->isInvalidDecl())
+      return StmtError();
     // In C++1y, the return type may involve 'auto'.
     // FIXME: Blocks might have a return type of 'auto' explicitly specified.
-    FunctionDecl *FD = CurLambda->CallOperator;
     if (CurCap->ReturnType.isNull())
       CurCap->ReturnType = FD->getReturnType();
 
diff --git a/clang/test/SemaCXX/lambda-expressions.cpp b/clang/test/SemaCXX/lambda-expressions.cpp
--- a/clang/test/SemaCXX/lambda-expressions.cpp
+++ b/clang/test/SemaCXX/lambda-expressions.cpp
@@ -521,6 +521,10 @@
       return undeclared_error; // expected-error {{use of undeclared identifier}}
     return 0;
   };
+  auto bar = []() {
+    return undef(); // expected-error {{use of undeclared identifier}}
+    return 0; // verify no init_conversion_failed diagnostic emitted.
+  };
 }
 }