diff --git a/src/utils/conftree.h b/src/utils/conftree.h
index f0335870..337dc9e4 100644
--- a/src/utils/conftree.h
+++ b/src/utils/conftree.h
@@ -52,6 +52,7 @@
 #include <string>
 #include <map>
 #include <vector>
+#include <algorithm>
 
 // rh7.3 likes iostream better...
 #if defined(__GNUC__) && __GNUC__ < 3