diff --git a/src/Base/PreCompiled.h b/src/Base/PreCompiled.h
index 4faa87df2d..79566cc4d0 100644
--- a/src/Base/PreCompiled.h
+++ b/src/Base/PreCompiled.h
@@ -66,6 +66,7 @@
 #include <string>
 #include <list>
 #include <map>
+#include <unordered_map>
 #include <vector>
 #include <set>
 #include <stack>