diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index af4c95040..81e37f626 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -2209,7 +2209,7 @@ AddCompilerRequirementFlag(std::string &flags, cmTarget* target,
     }
   const char* defaultStd
       = this->Makefile->GetDefinition("CMAKE_" + lang + "_STANDARD_DEFAULT");
-  if (defaultStd && !*defaultStd)
+  if (!defaultStd || !*defaultStd)
     {
     // This compiler has no notion of language standard levels.
     return;
@@ -2276,15 +2276,15 @@ AddCompilerRequirementFlag(std::string &flags, cmTarget* target,
                                 std::find(stds.begin(), stds.end(), standard);
   assert(stdIt != stds.end());
 
-  std::vector<std::string>::const_iterator defaultStdIt;
-  if (defaultStd)
+  std::vector<std::string>::const_iterator defaultStdIt =
+    std::find(stds.begin(), stds.end(), defaultStd);
+  if (defaultStdIt == stds.end())
     {
-    defaultStdIt = std::find(stds.begin(), stds.end(), defaultStd);
-    assert(defaultStdIt != stds.end());
-    }
-  else
-    {
-    defaultStdIt = stds.end() - 1;
+    std::string e =
+      "CMAKE_" + lang + "_STANDARD_DEFAULT is set to invalid value '" +
+      std::string(defaultStd) + "'";
+    this->Makefile->IssueMessage(cmake::INTERNAL_ERROR, e);
+    return;
     }
 
   for ( ; stdIt <= defaultStdIt; ++stdIt)