diff --git a/src/os.cc b/src/os.cc
index 0eab6f98c..e02835acd 100644
--- a/src/os.cc
+++ b/src/os.cc
@@ -26,6 +26,7 @@
 
 #include <cerrno>
 #include <cstdlib>
+#include <cstring>  // for std::strlen
 #include <algorithm>
 
 #ifndef _WIN32