diff --git a/src/commandlineflags.cc b/src/commandlineflags.cc
index 7cd64d22..aeb27ec9 100644
--- a/src/commandlineflags.cc
+++ b/src/commandlineflags.cc
@@ -17,6 +17,7 @@
 #include <cstring>
 #include <iostream>
 #include <limits>
+#include <cstdlib>
 
 namespace benchmark {
 // Parses 'str' for a 32-bit signed integer.  If successful, writes