diff --git a/ethosu/regor/compiler/graph_builder.hpp b/ethosu/regor/compiler/graph_builder.hpp
index 932f550e08098d98ed02b67fdd28575db029a09b..329e23bbd56de7a747afd6b8041c9ea1e4d935d4 100644
--- a/ethosu/regor/compiler/graph_builder.hpp
+++ b/ethosu/regor/compiler/graph_builder.hpp
@@ -25,6 +25,7 @@
 
 #include <memory>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 namespace regor