diff --git a/http.c b/http.c
index 6da05592..128136c8 100644
--- a/http.c
+++ b/http.c
@@ -44,7 +44,7 @@ struct oc_text_buf *buf_alloc(void)
 	return calloc(1, sizeof(struct oc_text_buf));
 }
 
-static int buf_ensure_space(struct oc_text_buf *buf, int len)
+int buf_ensure_space(struct oc_text_buf *buf, int len)
 {
 	int new_buf_len;
 
diff --git a/openconnect-internal.h b/openconnect-internal.h
index 08ccfff7..afd3a725 100644
--- a/openconnect-internal.h
+++ b/openconnect-internal.h
@@ -582,6 +582,7 @@ int prepare_stoken(struct openconnect_info *vpninfo);
 
 /* http.c */
 struct oc_text_buf *buf_alloc(void);
+int buf_ensure_space(struct oc_text_buf *buf, int len);
 void  __attribute__ ((format (printf, 2, 3)))
 	buf_append(struct oc_text_buf *buf, const char *fmt, ...);
 void buf_append_bytes(struct oc_text_buf *buf, const void *bytes, int len);