diff --git a/m4/include_next.m4 b/m4/include_next.m4
index ebf081a..62bdc77 100644
--- a/m4/include_next.m4
+++ b/m4/include_next.m4
@@ -212,8 +212,8 @@ dnl until we can assume autoconf 2.64 or newer.
                dnl so use subshell.
                AS_VAR_SET(gl_next_header,
                  ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
-                  sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{
-                    s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#
+                  sed -n '\#[\\/]]m4_defn([gl_HEADER_NAME])[#{
+                    s#.*"\(.*[\\/]]m4_defn([gl_HEADER_NAME])[\)".*#\1#
                     s#^/[^/]#//&#
                     p
                     q