diff --git a/dtool/Config.pp b/dtool/Config.pp
index f5e059d845..29e9e58416 100644
--- a/dtool/Config.pp
+++ b/dtool/Config.pp
@@ -190,7 +190,7 @@
 // directory (presumably so you can develop them and make changes
 // without having to reinstall), comment out this definition and put
 // your source directory on your PYTHONPATH.
-//#define INSTALL_PYTHON_SOURCE 1
+#define INSTALL_PYTHON_SOURCE 1
 
 // Do you want to enable the "in_interpreter" global variable?  This
 // will enable some callbacks, particularly the MemoryUsage object, to