diff --git a/mysql-test/r/func_regexp.result b/mysql-test/r/func_regexp.result
index f405a2297cb..53c58d5dddb 100644
--- a/mysql-test/r/func_regexp.result
+++ b/mysql-test/r/func_regexp.result
@@ -145,3 +145,15 @@ a
 DEALLOCATE PREPARE stmt1;
 DROP TABLE t1;
 End of 5.1 tests
+SELECT ' '  REGEXP '[[:blank:]]';
+' '  REGEXP '[[:blank:]]'
+1
+SELECT '\t' REGEXP '[[:blank:]]';
+'\t' REGEXP '[[:blank:]]'
+1
+SELECT ' '  REGEXP '[[:space:]]';
+' '  REGEXP '[[:space:]]'
+1
+SELECT '\t' REGEXP '[[:space:]]';
+'\t' REGEXP '[[:space:]]'
+1
diff --git a/mysql-test/t/func_regexp.test b/mysql-test/t/func_regexp.test
index 638e0bf08ee..d0ab0cc9044 100644
--- a/mysql-test/t/func_regexp.test
+++ b/mysql-test/t/func_regexp.test
@@ -92,3 +92,15 @@ DROP TABLE t1;
 
 
 --echo End of 5.1 tests
+
+#
+# MDEV-5820 MySQL Bug #54805 definitions in regex/my_regex.h conflict with /usr/include/regex.h
+# Bug #55427 REGEXP does not recognize '\t' as [:blank:]
+#
+# Test that \t is indeed recognized as [[:blank:]]
+#
+SELECT ' '  REGEXP '[[:blank:]]';
+SELECT '\t' REGEXP '[[:blank:]]';
+
+SELECT ' '  REGEXP '[[:space:]]';
+SELECT '\t' REGEXP '[[:space:]]';