diff --git a/lib/imap.c b/lib/imap.c
index ccfbeb72c4..21143fb63f 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -1453,7 +1453,7 @@ static CURLcode imap_state_fetch_resp(struct Curl_easy *data,
         return result;
 
       infof(data, "Written %zu bytes, %" FMT_OFF_TU
-            " bytes are left for transfer", chunk, size - chunk);
+            " bytes are left for transfer", chunk, (curl_off_t)(size - chunk));
 
       /* Have we used the entire overflow or part of it?*/
       if(pp->overflow > chunk) {