diff --git a/lib/vauth/digest_sspi.c b/lib/vauth/digest_sspi.c
index 15f3d8c14b..a6eea5ca64 100644
--- a/lib/vauth/digest_sspi.c
+++ b/lib/vauth/digest_sspi.c
@@ -412,7 +412,7 @@ CURLcode Curl_auth_create_digest_http_message(struct Curl_easy *data,
   size_t token_max;
   char *resp;
   BYTE *output_token;
-  size_t output_token_len;
+  size_t output_token_len = 0;
   PSecPkgInfo SecurityPackage;
   SecBuffer chlg_buf[5];
   SecBufferDesc chlg_desc;