diff --git a/common/fs.cc b/common/fs.cc
index 9e320027..68b486e0 100644
--- a/common/fs.cc
+++ b/common/fs.cc
@@ -27,6 +27,7 @@
 #include <list>
 #include <set>
 #include <stdexcept>
+#include <unordered_map>
 
 namespace fs
 {