diff --git a/doc/GNUmakefile b/doc/GNUmakefile
index 0686f30..4b9c4a2 100644
--- a/doc/GNUmakefile
+++ b/doc/GNUmakefile
@@ -29,3 +29,5 @@ include $(SRCROOT)/doc/etc/tailcat.mk
 
 clobber::
 	-/bin/rm -rf $(OUTPUT_DIR)
+
+# non-substantive comment for commits mail test