diff --git a/conftest.err b/conftest.err
new file mode 100644
index 0000000..7040a2c
--- /dev/null
+++ b/conftest.err
@@ -0,0 +1,7 @@
+conftest.cpp:23:9: warning: 'BISON_VERSION' macro redefined [-Wmacro-redefined]
+#define BISON_VERSION 3.8.2
+        ^
+conftest.cpp:22:9: note: previous definition is here
+#define BISON_VERSION 0.0
+        ^
+1 warning generated.