diff --git a/gtsam_unstable/partition/GenericGraph.cpp b/gtsam_unstable/partition/GenericGraph.cpp
index d845c9a84..4d9bf4f63 100644
--- a/gtsam_unstable/partition/GenericGraph.cpp
+++ b/gtsam_unstable/partition/GenericGraph.cpp
@@ -6,6 +6,7 @@
  *  Description: generic graph types used in partitioning
  */
 #include <iostream>
+#include <cassert>
 
 #include <gtsam/base/DSFVector.h>