diff --git a/panda/src/express/memoryUsage.cxx b/panda/src/express/memoryUsage.cxx
index d5e039d484..9061aab12d 100644
--- a/panda/src/express/memoryUsage.cxx
+++ b/panda/src/express/memoryUsage.cxx
@@ -27,6 +27,7 @@
 #endif
 
 #include "config_express.h"
+#include "configVariableInt64.h"
 #include <algorithm>
 #include <iterator>