diff --git a/googlemock/include/gmock/gmock-spec-builders.h b/googlemock/include/gmock/gmock-spec-builders.h
index 1f261bd2..255d6ad6 100644
--- a/googlemock/include/gmock/gmock-spec-builders.h
+++ b/googlemock/include/gmock/gmock-spec-builders.h
@@ -61,6 +61,7 @@
 #ifndef GMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
 #define GMOCK_INCLUDE_GMOCK_GMOCK_SPEC_BUILDERS_H_
 
+#include <functional>
 #include <map>
 #include <memory>
 #include <set>