diff --git a/docs/reference/Makefile.am b/docs/reference/Makefile.am
index 7c37193..6b711d2 100644
--- a/docs/reference/Makefile.am
+++ b/docs/reference/Makefile.am
@@ -100,7 +100,7 @@ AM_LDFLAGS += \
 # This is extracted from gtk-doc.make
 if GTK_DOC_USE_LIBTOOL
 override GTKDOC_RUN = \
-	$(gtkdoc_run_prefix) $(LIBTOOL) --mode=execute
+	env $(gtkdoc_run_prefix) $(LIBTOOL) --mode=execute
 else
 override GTKDOC_RUN = \
 	$(gtkdoc_run_prefix) sh -c