diff --git a/Parser/pgen.h b/Parser/pgen.h
index dd761609953..46d81ff8fdc 100644
--- a/Parser/pgen.h
+++ b/Parser/pgen.h
@@ -27,4 +27,6 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 extern grammar gram;
 
 extern grammar *meta_grammar PROTO((void));
+
+struct _node;
 extern grammar *pgen PROTO((struct _node *));