diff --git a/src/openvpn/auth_token.c b/src/openvpn/auth_token.c
index e8875464..ceae68f6 100644
--- a/src/openvpn/auth_token.c
+++ b/src/openvpn/auth_token.c
@@ -259,7 +259,7 @@ generate_auth_token(const struct user_pass *up, struct tls_multi *multi)
     ASSERT(buf_write(&token, &timestamp, sizeof(timestamp)));
     ASSERT(buf_write(&token, hmac_output, sizeof(hmac_output)));
 
-    char *b64output;
+    char *b64output = NULL;
     openvpn_base64_encode(BPTR(&token), BLEN(&token), &b64output);
 
     struct buffer session_token = alloc_buf_gc(