diff --git a/src/pl/plpython/Makefile b/src/pl/plpython/Makefile
index df07fc2ced..1b1259feef 100644
--- a/src/pl/plpython/Makefile
+++ b/src/pl/plpython/Makefile
@@ -131,7 +131,7 @@ prep3:
 	      -e "s/LANGUAGE plpython2u/LANGUAGE plpython3u/g" \
 	      -e "s/EXTENSION plpythonu/EXTENSION plpython3u/g" \
 	      -e "s/EXTENSION plpython2u/EXTENSION plpython3u/g" \
-	    $$file >`echo $$file | sed 's,$(srcdir),python3,'` || exit; \
+	    $$file >`echo $$file | sed 's,^.*\(/[^/][^/]*/[^/][^/]*\)$$,python3\1,'` || exit; \
 	done
 
 clean3: