diff --git a/markdown-mode.el b/markdown-mode.el
index 0ea969be..2f084c8f 100644
--- a/markdown-mode.el
+++ b/markdown-mode.el
@@ -1277,7 +1277,7 @@ Group 2 matches only the label, without the surrounding markup.
 Group 3 matches the closing square bracket.")
 
 (defconst markdown-regex-header
-  "^\\(?:\\([^\r\n- ].*\\)\n\\(?:\\(=+\\)\\|\\(-+\\)\\)\\|\\(#+\\)[ \t]+\\(.*?\\)[ \t]*\\(#*\\)\\)$"
+  "^\\(?:\\([^\r\n\t -].*\\)\n\\(?:\\(=+\\)\\|\\(-+\\)\\)\\|\\(#+\\)[ \t]+\\(.*?\\)[ \t]*\\(#*\\)\\)$"
   "Regexp identifying Markdown headings.
 Group 1 matches the text of a setext heading.
 Group 2 matches the underline of a level-1 setext heading.
@@ -1287,7 +1287,7 @@ Group 5 matches the text, without surrounding whitespace, of an atx heading.
 Group 6 matches the closing hash marks of an atx heading.")
 
 (defconst markdown-regex-header-setext
-  "^\\([^\r\n- ].*\\)\n\\(=+\\|-+\\)$"
+  "^\\([^\r\n\t -].*\\)\n\\(=+\\|-+\\)$"
   "Regular expression for generic setext-style (underline) headers.")
 
 (defconst markdown-regex-header-atx