diff --git a/ext/theora/gsttheoraenc.c b/ext/theora/gsttheoraenc.c
index 8960dfc61a..bd9b6aa5de 100644
--- a/ext/theora/gsttheoraenc.c
+++ b/ext/theora/gsttheoraenc.c
@@ -851,7 +851,7 @@ theora_enc_buffer_from_header_packet (GstTheoraEnc * enc, ogg_packet * packet)
   GST_BUFFER_TIMESTAMP (outbuf) = GST_CLOCK_TIME_NONE;
   GST_BUFFER_DURATION (outbuf) = GST_CLOCK_TIME_NONE;
 
-  GST_DEBUG ("created header packet buffer, %d bytes",
+  GST_DEBUG ("created header packet buffer, %zu bytes",
       gst_buffer_get_size (outbuf));
   return outbuf;
 }