1 files changed, 1 insertions, 0 deletions
diff --git a/intern.h b/intern.h
index d9180183e5..1c55a07390 100644
--- a/intern.h
+++ b/intern.h
@@ -243,6 +243,7 @@ int rb_during_gc _((void));
 char *rb_source_filename _((const char*));
 void rb_gc_mark_locations _((VALUE*, VALUE*));
 void rb_mark_tbl _((struct st_table*));
+void rb_mark_set _((struct st_table*));
 void rb_mark_hash _((struct st_table*));
 void rb_gc_mark_maybe _((VALUE));
 void rb_gc_mark _((VALUE));