diff --git a/version.h b/version.h
index 3a11ea1cce..2a80d6c910 100644
--- a/version.h
+++ b/version.h
@@ -49,7 +49,7 @@
 #ifdef RUBY_REVISION
 # if RUBY_PATCHLEVEL == -1
 #  ifndef RUBY_BRANCH_NAME
-#   define RUBY_BRANCH_NAME "trunk"
+#   define RUBY_BRANCH_NAME "master"
 #  endif
 #  define RUBY_REVISION_STR " "RUBY_BRANCH_NAME" "RUBY_REVISION
 # else