diff --git a/src/libutil/strings.cc b/src/libutil/strings.cc
index d1c9f700c..c221a43c6 100644
--- a/src/libutil/strings.cc
+++ b/src/libutil/strings.cc
@@ -1,5 +1,6 @@
 #include <filesystem>
 #include <string>
+#include <sstream>
 
 #include "strings-inline.hh"
 #include "os-string.hh"