diff --git a/Source/cmStateTypes.h b/Source/cmStateTypes.h
index 2c974c1dc0..da14cdb30e 100644
--- a/Source/cmStateTypes.h
+++ b/Source/cmStateTypes.h
@@ -27,6 +27,9 @@ enum SnapshotType
   VariableScopeType
 };
 
+// There are multiple overlapping ranges represented here. Be aware that adding
+// a value to this enumeration may cause failures in numerous places which
+// assume details about the ordering.
 enum TargetType
 {
   EXECUTABLE,