diff --git a/lib/fko_encode.c b/lib/fko_encode.c
index c92d421..ab150df 100644
--- a/lib/fko_encode.c
+++ b/lib/fko_encode.c
@@ -115,7 +115,7 @@ fko_encode_spa_data(fko_ctx_t ctx)
     /* Add the timestamp.
     */
     offset = strlen(tbuf);
-    sprintf(((char*)tbuf+offset), ":%u:", (unsigned int) ctx->timestamp);
+    sprintf(((char*)tbuf+offset), "::%u:", (unsigned int) ctx->timestamp);
 
     /* Add the version string.
     */