--- a/src/http/ngx_http_variables.h
+++ b/src/http/ngx_http_variables.h
@@ -61,6 +61,10 @@ ngx_http_variable_value_t *ngx_http_get_
 ngx_http_variable_value_t *ngx_http_get_variable(ngx_http_request_t *r,
     ngx_str_t *name, ngx_uint_t key, ngx_uint_t nowarn);
 
+ngx_int_t ngx_http_variable_unknown_header(ngx_http_variable_value_t *v,
+    ngx_str_t *var, ngx_list_part_t *part, size_t prefix);
+
+
 #define ngx_http_clear_variable(r, index) r->variables0[index].text.data = NULL;