diff --git a/src/misc/dstring.c b/src/misc/dstring.c
index 3706134b4..ccee090e6 100644
--- a/src/misc/dstring.c
+++ b/src/misc/dstring.c
@@ -277,7 +277,7 @@ int ds_cat_vprintf(DSTRING *p_ds, const char *sz_fmt, va_list p_arg)
     }
 
     /* Else check for buffer large enough and set length if it is */
-    if (rc < n_byte_free) {
+    if ((size_t) rc < n_byte_free) {
         p_ds->length += rc;
         return DS_E_OK;
     }