=== modified file 'mysql-test/r/func_regexp.result'
--- mysql-test/r/func_regexp.result	2014-02-22 21:51:20 +0000
+++ mysql-test/r/func_regexp.result	2014-03-11 09:04:57 +0000
@@ -145,3 +145,15 @@ EXECUTE stmt1;
 DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
 End of 5.1 tests
+SELECT ' '  REGEXP '[[:blank:]]';
+' '  REGEXP '[[:blank:]]'
+1
+SELECT '\t' REGEXP '[[:blank:]]';
+'\t' REGEXP '[[:blank:]]'
+0
+SELECT ' '  REGEXP '[[:space:]]';
+' '  REGEXP '[[:space:]]'
+1
+SELECT '\t' REGEXP '[[:space:]]';
+'\t' REGEXP '[[:space:]]'
+1

=== modified file 'mysql-test/t/func_regexp.test'
--- mysql-test/t/func_regexp.test	2008-09-05 08:36:02 +0000
+++ mysql-test/t/func_regexp.test	2014-03-11 09:04:57 +0000
@@ -92,3 +92,17 @@ DROP TABLE t1;
 
 
 --echo End of 5.1 tests
+
+#
+# Bug #54805 definitions in regex/my_regex.h conflict with /usr/include/regex.h
+#
+# This test verifies that '\t' is recognized as space, but not as blank.
+# This is *not* according to the POSIX standard, but seems to have been MySQL
+# behaviour ever since regular expressions were introduced.
+# See: Bug #55427 REGEXP does not recognize '\t' as [:blank:]
+#
+SELECT ' '  REGEXP '[[:blank:]]';
+SELECT '\t' REGEXP '[[:blank:]]';
+
+SELECT ' '  REGEXP '[[:space:]]';
+SELECT '\t' REGEXP '[[:space:]]';