diff --git a/runtime/base/stl_util.h b/runtime/base/stl_util.h
index a53dcea..d5f375a 100644
--- a/runtime/base/stl_util.h
+++ b/runtime/base/stl_util.h
@@ -18,6 +18,7 @@
 #define ART_RUNTIME_BASE_STL_UTIL_H_
 
 #include <algorithm>
+#include <set>
 #include <sstream>
 
 #include "base/logging.h"
@@ -187,6 +188,12 @@
   using type = T;
 };
 
+// Merge `other` entries into `to_update`.
+template <typename T>
+static inline void MergeSets(std::set<T>& to_update, const std::set<T>& other) {
+  to_update.insert(other.begin(), other.end());
+}
+
 }  // namespace art
 
 #endif  // ART_RUNTIME_BASE_STL_UTIL_H_