diff --git a/test_conformance/subgroups/subhelpers.cpp b/test_conformance/subgroups/subhelpers.cpp
index 440cde20..0899ef9c 100644
--- a/test_conformance/subgroups/subhelpers.cpp
+++ b/test_conformance/subgroups/subhelpers.cpp
@@ -16,6 +16,7 @@
 
 #include "subhelpers.h"
 
+#include <algorithm>
 #include <random>
 
 // Define operator<< for cl_ types, accessing the .s member.