Index: wp-includes/shortcodes.php
===================================================================
--- wp-includes/shortcodes.php	(revision 21302)
+++ wp-includes/shortcodes.php	(working copy)
@@ -181,7 +181,7 @@
 		  '\\['                              // Opening bracket
 		. '(\\[?)'                           // 1: Optional second opening bracket for escaping shortcodes: [[tag]]
 		. "($tagregexp)"                     // 2: Shortcode name
-		. '\\b'                              // Word boundary
+		. '(?![\\w-])'                       // Word boundary
 		. '('                                // 3: Unroll the loop: Inside the opening shortcode tag
 		.     '[^\\]\\/]*'                   // Not a closing bracket or forward slash
 		.     '(?:'
Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 21302)
+++ wp-includes/formatting.php	(working copy)
@@ -295,7 +295,7 @@
 		. '('                                // 1: The shortcode
 		.     '\\['                          // Opening bracket
 		.     "($tagregexp)"                 // 2: Shortcode name
-		.     '\\b'                          // Word boundary
+		.     '(?![\\w-])'                   // Word boundary
 		                                     // Unroll the loop: Inside the opening shortcode tag
 		.     '[^\\]\\/]*'                   // Not a closing bracket or forward slash
 		.     '(?:'