diff --git a/mysql-test/r/null.result b/mysql-test/r/null.result
index 1425b2a7f89..18eb10f0673 100644
--- a/mysql-test/r/null.result
+++ b/mysql-test/r/null.result
@@ -278,3 +278,45 @@ field('str1', null, 'STR1') as c05,
 c01	c02	c03	c04	c05	c08	c09
 str	str	0	1	2	1	1
 set names latin1;
+create table bug19145a (e enum('a','b','c')          default 'b' , s set('x', 'y', 'z')          default 'y' ) engine=MyISAM;
+create table bug19145b (e enum('a','b','c')          default null, s set('x', 'y', 'z')          default null) engine=MyISAM;
+create table bug19145c (e enum('a','b','c') not null default 'b' , s set('x', 'y', 'z') not null default 'y' ) engine=MyISAM;
+create table bug19145setnotnulldefaultnull (e enum('a','b','c')          default null, s set('x', 'y', 'z') not null default null) engine=MyISAM;
+ERROR 42000: Invalid default value for 's'
+create table bug19145enumnotnulldefaultnull (e enum('a','b','c') not null default null, s set('x', 'y', 'z')          default null) engine=MyISAM;
+ERROR 42000: Invalid default value for 'e'
+alter table bug19145a alter column e set default null;
+alter table bug19145a alter column s set default null;
+alter table bug19145a add column (i int);
+alter table bug19145b alter column e set default null;
+alter table bug19145b alter column s set default null;
+alter table bug19145b add column (i int);
+alter table bug19145c alter column e set default null;
+ERROR 42000: Invalid default value for 'e'
+alter table bug19145c alter column s set default null;
+ERROR 42000: Invalid default value for 's'
+alter table bug19145c add column (i int);
+show create table bug19145a;
+Table	Create Table
+bug19145a	CREATE TABLE `bug19145a` (
+  `e` enum('a','b','c') default NULL,
+  `s` set('x','y','z') default NULL,
+  `i` int(11) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+show create table bug19145b;
+Table	Create Table
+bug19145b	CREATE TABLE `bug19145b` (
+  `e` enum('a','b','c') default NULL,
+  `s` set('x','y','z') default NULL,
+  `i` int(11) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+show create table bug19145c;
+Table	Create Table
+bug19145c	CREATE TABLE `bug19145c` (
+  `e` enum('a','b','c') NOT NULL default 'b',
+  `s` set('x','y','z') NOT NULL default 'y',
+  `i` int(11) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table bug19145a;
+drop table bug19145b;
+drop table bug19145c;
diff --git a/mysql-test/t/null.test b/mysql-test/t/null.test
index 183308880ed..4aec745f3f7 100644
--- a/mysql-test/t/null.test
+++ b/mysql-test/t/null.test
@@ -190,4 +190,45 @@ select
 # Restore charset to the default value.
 set names latin1;
 
+#
+# Bug#19145: mysqld crashes if you set the default value of an enum field to NULL
+#
+create table bug19145a (e enum('a','b','c')          default 'b' , s set('x', 'y', 'z')          default 'y' ) engine=MyISAM;
+create table bug19145b (e enum('a','b','c')          default null, s set('x', 'y', 'z')          default null) engine=MyISAM;
+
+create table bug19145c (e enum('a','b','c') not null default 'b' , s set('x', 'y', 'z') not null default 'y' ) engine=MyISAM;
+
+# Invalid default value for 's'
+--error 1067
+create table bug19145setnotnulldefaultnull (e enum('a','b','c')          default null, s set('x', 'y', 'z') not null default null) engine=MyISAM;
+
+# Invalid default value for 'e'
+--error 1067
+create table bug19145enumnotnulldefaultnull (e enum('a','b','c') not null default null, s set('x', 'y', 'z')          default null) engine=MyISAM;
+
+alter table bug19145a alter column e set default null;
+alter table bug19145a alter column s set default null;
+alter table bug19145a add column (i int);
+
+alter table bug19145b alter column e set default null;
+alter table bug19145b alter column s set default null;
+alter table bug19145b add column (i int);
+
+# Invalid default value for 'e'
+--error 1067
+alter table bug19145c alter column e set default null;
+
+# Invalid default value for 's'
+--error 1067
+alter table bug19145c alter column s set default null;
+alter table bug19145c add column (i int);
+
+show create table bug19145a;
+show create table bug19145b;
+show create table bug19145c;
+
+drop table bug19145a;
+drop table bug19145b;
+drop table bug19145c;
+
 # End of 4.1 tests
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index cb556acd5c7..073a847ad90 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -799,7 +799,7 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
         if (need_to_change_arena)
           thd->restore_active_arena(thd->stmt_arena, &backup_arena);
 
-        if (! sql_field->def)
+        if (sql_field->def == NULL)
         {
           /* Could not convert */
           my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
@@ -810,15 +810,30 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
       if (sql_field->sql_type == FIELD_TYPE_SET)
       {
         uint32 field_length;
-        if (sql_field->def)
+        if (sql_field->def != NULL)
         {
           char *not_used;
           uint not_used2;
           bool not_found= 0;
           String str, *def= sql_field->def->val_str(&str);
-          def->length(cs->cset->lengthsp(cs, def->ptr(), def->length()));
-          (void) find_set(interval, def->ptr(), def->length(),
-                          cs, &not_used, &not_used2, &not_found);
+          if (def == NULL) /* SQL "NULL" maps to NULL */
+          {
+            if ((sql_field->flags & NOT_NULL_FLAG) != 0)
+            {
+              my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
+              DBUG_RETURN(-1);
+            }
+
+            /* else, NULL is an allowed value */
+            (void) find_set(interval, NULL, 0,
+                            cs, &not_used, &not_used2, &not_found);
+          }
+          else /* not NULL */
+          {
+            (void) find_set(interval, def->ptr(), def->length(),
+                            cs, &not_used, &not_used2, &not_found);
+          }
+
           if (not_found)
           {
             my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
@@ -831,14 +846,28 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
       else  /* FIELD_TYPE_ENUM */
       {
         uint32 field_length;
-        if (sql_field->def)
+        DBUG_ASSERT(sql_field->sql_type == FIELD_TYPE_ENUM);
+        if (sql_field->def != NULL)
         {
           String str, *def= sql_field->def->val_str(&str);
-          def->length(cs->cset->lengthsp(cs, def->ptr(), def->length()));
-          if (!find_type2(interval, def->ptr(), def->length(), cs))
+          if (def == NULL) /* SQL "NULL" maps to NULL */
           {
-            my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
-            DBUG_RETURN(-1);
+            if ((sql_field->flags & NOT_NULL_FLAG) != 0)
+            {
+              my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
+              DBUG_RETURN(-1);
+            }
+
+            /* else, the defaults yield the correct length for NULLs. */
+          } 
+          else /* not NULL */
+          {
+            def->length(cs->cset->lengthsp(cs, def->ptr(), def->length()));
+            if (find_type2(interval, def->ptr(), def->length(), cs) == 0) /* not found */
+            {
+              my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
+              DBUG_RETURN(-1);
+            }
           }
         }
         calculate_interval_lengths(cs, interval, &field_length, &dummy);