diff --git a/mysql-test/r/alter_table.result b/mysql-test/r/alter_table.result
index 06f4e7fbe8a..004e2031fb1 100644
--- a/mysql-test/r/alter_table.result
+++ b/mysql-test/r/alter_table.result
@@ -1338,4 +1338,11 @@ ALTER TABLE t1 CHANGE COLUMN f1 f1_no_real_change TIMESTAMP NULL DEFAULT NULL;
 affected rows: 0
 info: Records: 0  Duplicates: 0  Warnings: 0
 DROP TABLE t1;
+#
+# Bug #31145: ALTER TABLE DROP COLUMN, ADD COLUMN crashes (linux) 
+#   or freezes (win) the server
+#
+CREATE TABLE t1 (a TEXT, id INT, b INT);
+ALTER TABLE t1 DROP COLUMN a, ADD COLUMN c TEXT FIRST;
+DROP TABLE t1;
 End of 5.1 tests
diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
index 5534aa0a234..4989a6c380c 100644
--- a/mysql-test/t/alter_table.test
+++ b/mysql-test/t/alter_table.test
@@ -1061,4 +1061,16 @@ ALTER TABLE t1 CHANGE COLUMN f1 f1_no_real_change TIMESTAMP NULL DEFAULT NULL;
 --disable_info
 DROP TABLE t1;
 
+
+--echo #
+--echo # Bug #31145: ALTER TABLE DROP COLUMN, ADD COLUMN crashes (linux) 
+--echo #   or freezes (win) the server
+--echo #
+
+CREATE TABLE t1 (a TEXT, id INT, b INT);
+ALTER TABLE t1 DROP COLUMN a, ADD COLUMN c TEXT FIRST;
+
+DROP TABLE t1;
+
+
 --echo End of 5.1 tests
diff --git a/sql/field.cc b/sql/field.cc
index 01ccc338782..d8db3fdbae4 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -8282,8 +8282,7 @@ uint Field_blob::is_equal(Create_field *new_field)
 
   return ((new_field->sql_type == get_blob_type_from_length(max_data_length()))
           && new_field->charset == field_charset &&
-          ((Field_blob *)new_field->field)->max_data_length() ==
-          max_data_length());
+          new_field->pack_length == pack_length());
 }