diff --git a/nix/libstore/local-store.cc b/nix/libstore/local-store.cc
index 11f61ae030..1eed0ca77f 100644
--- a/nix/libstore/local-store.cc
+++ b/nix/libstore/local-store.cc
@@ -606,10 +606,10 @@ static void canonicalisePathMetaData_(const Path & path, uid_t fromUid, InodesSe
        users group); we check for this case below. */
     if (st.st_uid != geteuid()) {
 #if HAVE_LCHOWN
-        if (lchown(path.c_str(), geteuid(), (gid_t) -1) == -1)
+        if (lchown(path.c_str(), geteuid(), getegid()) == -1)
 #else
         if (!S_ISLNK(st.st_mode) &&
-            chown(path.c_str(), geteuid(), (gid_t) -1) == -1)
+            chown(path.c_str(), geteuid(), getegid()) == -1)
 #endif
             throw SysError(format("changing owner of `%1%' to %2%")
                 % path % geteuid());