diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f3e8a34bd7584b68260ac08348a9a37eb955c239..eac53b89450d4b705d941aea348c1600ae09f5d4 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -7,6 +7,7 @@
 #include "hash.hh"
 #include "config.hh"
 
+#include <regex>
 #include <map>
 #include <optional>
 #include <unordered_map>