diff --git a/src/compiler/parser/pa_externfn.c b/src/compiler/parser/pa_externfn.c
index 66f6738..f6985b6 100644
--- a/src/compiler/parser/pa_externfn.c
+++ b/src/compiler/parser/pa_externfn.c
@@ -69,7 +69,6 @@ fzl_node_t *pa_externfn(fzl_parser_t *parser)
       consume(parser);
       is_out = true;
     }
-    (void)is_out;
 
     fzl_node_t *node = pa_expression(parser);
     if (!node || node->type != FZL_NODETYPE_DECLARATION)
@@ -86,7 +85,8 @@ fzl_node_t *pa_externfn(fzl_parser_t *parser)
       return NULL;
     }
 
-    args[count++] = node;
+    node->var.is_out = is_out;
+    args[count++]    = node;
 
     if (is(parser, FZL_TOKTYPE_RPAREN))
       break;