kc3-lang/md4c

diff --git a/src/md4c.c b/src/md4c.c
index f23b9d7..40066b2 100644
--- a/src/md4c.c
+++ b/src/md4c.c
@@ -5383,7 +5383,7 @@ md_is_html_block_start_condition(MD_CTX* ctx, OFF beg)
     /* Check for type 4 or 5: <! */
     if(off < ctx->size  &&  CH(off) == _T('!')) {
         /* Check for type 4: <! followed by uppercase letter. */
-        if(off + 1 < ctx->size  &&  ISUPPER(off+1))
+        if(off + 1 < ctx->size  &&  ISASCII(off+1))
             return 4;
 
         /* Check for type 5: <![CDATA[ */