--- a/cpp/src/arrow/filesystem/mockfs.cc
+++ b/cpp/src/arrow/filesystem/mockfs.cc
@@ -322,7 +322,9 @@ class MockFileSystem::Impl {
       return nullptr;
     }
     size_t consumed;
-    auto entry = FindEntry(parts.begin(), --parts.end(), &consumed);
+    auto last = parts.end();
+    last--;
+    auto entry = FindEntry(parts.begin(), last, &consumed);
     return (consumed == parts.size() - 1) ? entry : nullptr;
   }