diff --git a/src/libCStreamedXML/buffer.c b/src/libCStreamedXML/buffer.c
index 64ab0be..67032e8 100644
--- a/src/libCStreamedXML/buffer.c
+++ b/src/libCStreamedXML/buffer.c
@@ -30,6 +30,7 @@ static int buffer_strcat(struct csxml* ctx, struct csxml_buf* dest, const char*
     size_t req = strlen(src) + dest->len;
     while(req >= dest->size) if(do_realloc(ctx, dest)) return -1;
     strcat(dest->data, src);
+    dest->len = req;
     return 0;
 }