diff --git a/Source/cmOutputConverter.cxx b/Source/cmOutputConverter.cxx
index 5acae2f82..59fb2e9e1 100644
--- a/Source/cmOutputConverter.cxx
+++ b/Source/cmOutputConverter.cxx
@@ -22,6 +22,7 @@
 cmOutputConverter::cmOutputConverter(cmState::Snapshot snapshot)
   : StateSnapshot(snapshot), LinkScriptShell(false)
 {
+  assert(this->StateSnapshot.IsValid());
 }
 
 //----------------------------------------------------------------------------