diff --git a/src/test/permutation.cpp b/src/test/permutation.cpp
index 7a3dbdaed..f860f3b03 100644
--- a/src/test/permutation.cpp
+++ b/src/test/permutation.cpp
@@ -2,6 +2,7 @@
 #include <sstream>
 #include "util/permutation.h"
 #include "util/util.h"
+#include "util/debug.h"
 
 void swap(unsigned m1, unsigned m2) noexcept { std::swap(m1, m2); }