diff --git a/src/IECoreArnold/ShaderNetworkAlgo.cpp b/src/IECoreArnold/ShaderNetworkAlgo.cpp
index 4bf9593d5e..f8aa41461b 100644
--- a/src/IECoreArnold/ShaderNetworkAlgo.cpp
+++ b/src/IECoreArnold/ShaderNetworkAlgo.cpp
@@ -53,6 +53,8 @@
 #include "boost/lexical_cast.hpp"
 #include "boost/unordered_map.hpp"
 
+#include <unordered_map>
+
 using namespace std;
 using namespace Imath;
 using namespace IECore;