diff --git a/mkfile b/mkfile
index a446df4d..1e3f77b8 100644
--- a/mkfile
+++ b/mkfile
@@ -14,7 +14,7 @@ HFILES=include/chibi/sexp.h include/chibi/eval.h include/chibi/features.h includ
 
 include/chibi/install.h: mkfile
 	echo '#define sexp_default_module_path "'$MODDIR'"' > include/chibi/install.h
-	echo '#define sexp_so_extension ""' >> include/chibi/install.h
+	echo '#define sexp_so_extension ".no-such-file"' >> include/chibi/install.h
 	echo '#define sexp_platform "plan9"' >> include/chibi/install.h
 	echo '#define sexp_version "'`{cat VERSION}'"' >> include/chibi/install.h
 	echo '#define sexp_release_name "'`{cat RELEASE}'"' >> include/chibi/install.h