diff --git a/mysql-test/r/type_set.result b/mysql-test/r/type_set.result
index e36f21f2996..09531ec60d5 100644
--- a/mysql-test/r/type_set.result
+++ b/mysql-test/r/type_set.result
@@ -93,4 +93,14 @@ c
 1,2,3
 64
 DROP TABLE t1;
+CREATE TABLE t1 (
+set_unique_utf8 set ('a','b','c','d','e','f','g','h','i','j','k','l',
+'m','n','o','p','q','r','s','t','u','v','w','x',
+'y','z') CHARACTER SET utf8,
+unique (set_unique_utf8)
+);
+INSERT INTO t1 ( set_unique_utf8 ) VALUES ( '' );
+INSERT INTO t1 ( set_unique_utf8 ) VALUES ( '' );
+ERROR 23000: Duplicate entry '' for key 'set_unique_utf8'
+DROP TABLE t1;
 End of 5.0 tests
diff --git a/mysql-test/t/type_set.test b/mysql-test/t/type_set.test
index e98555e137b..a851d116743 100644
--- a/mysql-test/t/type_set.test
+++ b/mysql-test/t/type_set.test
@@ -75,4 +75,23 @@ INSERT INTO t1 VALUES(9223372036854775808);
 SELECT * FROM t1;
 DROP TABLE t1;
 
+#
+# Bug #38701: Crash in String::append when inserting duplicate empty strings
+# an uft8 SET col
+#
+
+CREATE TABLE t1 (
+        set_unique_utf8 set ('a','b','c','d','e','f','g','h','i','j','k','l',
+                             'm','n','o','p','q','r','s','t','u','v','w','x',
+                             'y','z') CHARACTER SET utf8,
+        unique (set_unique_utf8)
+);
+
+INSERT INTO t1 ( set_unique_utf8 ) VALUES ( '' );
+--error ER_DUP_ENTRY 
+INSERT INTO t1 ( set_unique_utf8 ) VALUES ( '' );
+
+DROP TABLE t1;
+
+
 --echo End of 5.0 tests
diff --git a/sql/handler.cc b/sql/handler.cc
index cc2db397ad4..f26e84bdfdf 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -2496,7 +2496,7 @@ void handler::print_keydup_error(uint key_nr, const char *msg)
       str.append(STRING_WITH_LEN("..."));
     }
     my_printf_error(ER_DUP_ENTRY, msg,
-		    MYF(0), str.c_ptr(), table->key_info[key_nr].name);
+		    MYF(0), str.c_ptr_safe(), table->key_info[key_nr].name);
   }
 }
 
@@ -2564,7 +2564,7 @@ void handler::print_error(int error, myf errflag)
         str.append(STRING_WITH_LEN("..."));
       }
       my_error(ER_FOREIGN_DUPLICATE_KEY, MYF(0), table_share->table_name.str,
-        str.c_ptr(), key_nr+1);
+        str.c_ptr_safe(), key_nr+1);
       DBUG_VOID_RETURN;
     }
     textno= ER_DUP_KEY;