diff --git a/variable.h b/variable.h
index 43972683..76af4c1d 100644
--- a/variable.h
+++ b/variable.h
@@ -98,3 +98,4 @@ extern int pattern_matches ();
 extern char *subst_expand (), *patsubst_expand ();
 
 extern char **target_environment ();
+extern int export_all_variables;