diff --git a/src/util/WritableBuffer.hxx b/src/util/WritableBuffer.hxx
index f9e6d4a96..71706b140 100644
--- a/src/util/WritableBuffer.hxx
+++ b/src/util/WritableBuffer.hxx
@@ -217,6 +217,15 @@ struct WritableBuffer {
 		pop_front();
 		return result;
 	}
+
+	void skip_front(size_type n) {
+#ifndef NDEBUG
+		assert(size >= n);
+#endif
+
+		data += n;
+		size -= n;
+	}
 };
 
 #endif