diff --git a/src/misc.c b/src/misc.c
index 1fb8780b..8d80456c 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -811,6 +811,9 @@ int _libssh2_get_bignum_bytes(struct string_buf *buf, unsigned char **outbuf)
 
 int _libssh2_check_length(struct string_buf *buf, size_t len)
 {
+    if(len > buf->len)
+        return 0;
+
     return ((int)(buf->dataptr - buf->data) <= (int)(buf->len - len)) ? 1 : 0;
 }