diff --git a/dtool/src/dtoolutil/config_dtoolutil.h b/dtool/src/dtoolutil/config_dtoolutil.h
index 20e9784c55..2d297937be 100644
--- a/dtool/src/dtoolutil/config_dtoolutil.h
+++ b/dtool/src/dtoolutil/config_dtoolutil.h
@@ -19,4 +19,6 @@
 // Include this so interrogate can find it.
 #include <iostream>
 
+extern EXPCL_DTOOL_DTOOLUTIL void init_libdtoolutil();
+
 #endif