diff --git a/block.go b/block.go
index ba84c67..8b2bfa0 100644
--- a/block.go
+++ b/block.go
@@ -335,7 +335,7 @@ func blockHtml(out *bytes.Buffer, rndr *render, data []byte, do_render bool) int
 
 func blockHtmlFindTag(data []byte) (string, bool) {
 	i := 0
-	for i < len(data) && ((data[i] >= '0' && data[i] <= '9') || (data[i] >= 'A' && data[i] <= 'Z') || (data[i] >= 'a' && data[i] <= 'z')) {
+	for i < len(data) && isalnum(data[i]) {
 		i++
 	}
 	if i >= len(data) {
@@ -352,11 +352,12 @@ func blockHtmlFindEnd(tag string, rndr *render, data []byte) int {
 	// assume data[0] == '<' && data[1] == '/' already tested
 
 	// check if tag is a match
-	if len(tag)+3 >= len(data) || bytes.Compare(data[2:2+len(tag)], []byte(tag)) != 0 || data[len(tag)+2] != '>' {
+	if len(data) < len(tag)+3 || data[len(tag)+2] != '>' ||
+		bytes.Compare(data[2:2+len(tag)], []byte(tag)) != 0 {
 		return 0
 	}
 
-	// check white lines
+	// check for blank line/eof after the closing tag
 	i := len(tag) + 3
 	w := 0
 	if i < len(data) {
diff --git a/block_test.go b/block_test.go
index 834a7e6..602879b 100644
--- a/block_test.go
+++ b/block_test.go
@@ -198,6 +198,9 @@ func TestUnderlineHeaders(t *testing.T) {
 
 		"Trailing spaces\n====        \n\n",
 		"<h1>Trailing spaces</h1>\n",
+
+		"Double underline\n=====\n=====\n",
+		"<h1>Double underline</h1>\n\n<p>=====</p>\n",
 	}
 	doTestsBlock(t, tests, 0)
 }
diff --git a/inline.go b/inline.go
index ae3fed1..1556022 100644
--- a/inline.go
+++ b/inline.go
@@ -123,9 +123,9 @@ func inlineCodeSpan(out *bytes.Buffer, rndr *render, data []byte, offset int) in
 		}
 	}
 
+	// no matching delimiter?
 	if i < nb && end >= len(data) {
-		out.WriteByte('`')
-		return 0 // no matching delimiter
+		return 0
 	}
 
 	// trim outside whitespace
@@ -135,22 +135,16 @@ func inlineCodeSpan(out *bytes.Buffer, rndr *render, data []byte, offset int) in
 	}
 
 	f_end := end - nb
-	for f_end > nb && (data[f_end-1] == ' ' || data[f_end-1] == '\t') {
+	for f_end > f_begin && (data[f_end-1] == ' ' || data[f_end-1] == '\t') {
 		f_end--
 	}
 
-	// real code span
+	// render the code span
 	if rndr.mk.CodeSpan == nil {
 		return 0
 	}
-	if f_begin < f_end {
-		if rndr.mk.CodeSpan(out, data[f_begin:f_end], rndr.mk.Opaque) == 0 {
-			end = 0
-		}
-	} else {
-		if rndr.mk.CodeSpan(out, nil, rndr.mk.Opaque) == 0 {
-			end = 0
-		}
+	if rndr.mk.CodeSpan(out, data[f_begin:f_end], rndr.mk.Opaque) == 0 {
+		end = 0
 	}
 
 	return end
diff --git a/inline_test.go b/inline_test.go
index 4f4f21e..81d21b9 100644
--- a/inline_test.go
+++ b/inline_test.go
@@ -16,19 +16,11 @@ import (
 
 func runMarkdownInline(input string) string {
 	var extensions uint32
-	extensions |= EXTENSION_NO_INTRA_EMPHASIS
-	extensions |= EXTENSION_TABLES
-	extensions |= EXTENSION_FENCED_CODE
 	extensions |= EXTENSION_AUTOLINK
 	extensions |= EXTENSION_STRIKETHROUGH
-	extensions |= EXTENSION_SPACE_HEADERS
-	extensions |= EXTENSION_LAX_HTML_BLOCKS
 
 	html_flags := 0
 	html_flags |= HTML_USE_XHTML
-	html_flags |= HTML_USE_SMARTYPANTS
-	html_flags |= HTML_SMARTYPANTS_FRACTIONS
-	html_flags |= HTML_SMARTYPANTS_LATEX_DASHES
 
 	renderer := HtmlRenderer(html_flags)