diff --git a/pandatool/src/maya/post_maya_include.h b/pandatool/src/maya/post_maya_include.h
index 9c3ee4b98c..888b5239c6 100644
--- a/pandatool/src/maya/post_maya_include.h
+++ b/pandatool/src/maya/post_maya_include.h
@@ -20,7 +20,7 @@
 // cleans up some of the definitions that it left open.
 
 // Remove the symbols defined from pre_maya_include.h.
-#ifndef MAYA_PRE_5_0
+#ifdef MAYA_PRE_5_0
 #undef ostream
 #undef istream
 #endif  // MAYA_PRE_5_0