diff --git a/panda/src/gsgbase/graphicsStateGuardianBase.cxx b/panda/src/gsgbase/graphicsStateGuardianBase.cxx
index e48c9de35d..df9970cda4 100644
--- a/panda/src/gsgbase/graphicsStateGuardianBase.cxx
+++ b/panda/src/gsgbase/graphicsStateGuardianBase.cxx
@@ -18,6 +18,7 @@
 
 #include "graphicsStateGuardianBase.h"
 #include "mutexHolder.h"
+#include <algorithm>
 
 GraphicsStateGuardianBase::GSGs GraphicsStateGuardianBase::_gsgs;
 GraphicsStateGuardianBase *GraphicsStateGuardianBase::_default_gsg;