diff --git a/src/wutil.cpp b/src/wutil.cpp
index 24069b398..c21fa199d 100644
--- a/src/wutil.cpp
+++ b/src/wutil.cpp
@@ -348,7 +348,7 @@ wchar_t *wrealpath(const wcstring &pathname, wchar_t *resolved_path) {
     if (narrow_res) {
         real_path.append(narrow_res);
     } else {
-        int pathsep_idx = narrow_path.rfind('/');
+        ssize_t pathsep_idx = narrow_path.rfind('/');
         if (pathsep_idx == 0) {
             // If the only pathsep is the first character then it's an absolute path with a
             // single path component and thus doesn't need conversion.