diff --git a/gerbview/excellon_image.h b/gerbview/excellon_image.h
index 4c7d14da64..d56e539718 100644
--- a/gerbview/excellon_image.h
+++ b/gerbview/excellon_image.h
@@ -40,8 +40,8 @@ enum drill_M_code_t {
     DRILL_M_TIPCHECK,
     DRILL_M_METRIC,
     DRILL_M_IMPERIAL,
-    DRILL_METRICHEADER,
-    DRILL_IMPERIALHEADER,
+    DRILL_METRIC_HEADER,
+    DRILL_IMPERIAL_HEADER,
     DRILL_DETECT_BROKEN,
     DRILL_INCREMENTALHEADER,
     DRILL_REWIND_STOP,