diff --git a/include/my_base.h b/include/my_base.h
index 168625f4a87..564cd833185 100644
--- a/include/my_base.h
+++ b/include/my_base.h
@@ -367,8 +367,11 @@ enum ha_base_keytype {
                                           given value */
 #define HA_ERR_RBR_LOGGING_FAILED 161  /* Row-based binlogging of row failed */
 #define HA_ERR_DROP_INDEX_FK      162  /* Index needed in foreign key constr. */
+#define HA_ERR_FOREIGN_DUPLICATE_KEY 163 /* Upholding foreign key constraints
+                                            would lead to a duplicate key
+                                            error in some other table. */
 
-#define HA_ERR_LAST               162  /* Copy last error no */
+#define HA_ERR_LAST               163  /* Copy last error no */
 
 /* Add error numbers before HA_ERR_LAST and change it accordingly. */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)
diff --git a/mysql-test/r/innodb.result b/mysql-test/r/innodb.result
index 577e6a7192a..30a19bdcba3 100644
--- a/mysql-test/r/innodb.result
+++ b/mysql-test/r/innodb.result
@@ -2758,3 +2758,21 @@ e varchar(255) character set utf8,
 key (a,b,c,d,e)) engine=innodb;
 ERROR 42000: Specified key was too long; max key length is 3072 bytes
 End of 5.0 tests
+CREATE TABLE t1 (
+field1 varchar(8) NOT NULL DEFAULT '',
+field2 varchar(8) NOT NULL DEFAULT '',
+PRIMARY KEY  (field1, field2)
+) ENGINE=InnoDB;
+CREATE TABLE t2 (
+field1 varchar(8) NOT NULL DEFAULT '' PRIMARY KEY,
+FOREIGN KEY (field1) REFERENCES t1 (field1)
+ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB;
+INSERT INTO t1 VALUES ('old', 'somevalu');
+INSERT INTO t1 VALUES ('other', 'anyvalue');
+INSERT INTO t2 VALUES ('old');
+INSERT INTO t2 VALUES ('other');
+UPDATE t1 SET field1 = 'other' WHERE field2 = 'somevalu';
+ERROR 23000: Upholding foreign key constraints for table 't1', entry 'other-somevalu', key 1 would lead to a duplicate entry
+DROP TABLE t2;
+DROP TABLE t1;
diff --git a/mysql-test/t/innodb.test b/mysql-test/t/innodb.test
index 10cb1dcf08b..ceffc3ada5b 100644
--- a/mysql-test/t/innodb.test
+++ b/mysql-test/t/innodb.test
@@ -1715,3 +1715,32 @@ create table t1 (a varchar(255) character set utf8,
                  key (a,b,c,d,e)) engine=innodb;
 
 --echo End of 5.0 tests
+
+#
+# Test that cascading updates leading to duplicate keys give the correct
+# error message (bug #9680)
+#
+
+CREATE TABLE t1 (
+  field1 varchar(8) NOT NULL DEFAULT '',
+  field2 varchar(8) NOT NULL DEFAULT '',
+  PRIMARY KEY  (field1, field2)
+) ENGINE=InnoDB;
+
+CREATE TABLE t2 (
+  field1 varchar(8) NOT NULL DEFAULT '' PRIMARY KEY,
+  FOREIGN KEY (field1) REFERENCES t1 (field1)
+    ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB;
+
+INSERT INTO t1 VALUES ('old', 'somevalu');
+INSERT INTO t1 VALUES ('other', 'anyvalue');
+
+INSERT INTO t2 VALUES ('old');
+INSERT INTO t2 VALUES ('other');
+
+--error ER_FOREIGN_DUPLICATE_KEY
+UPDATE t1 SET field1 = 'other' WHERE field2 = 'somevalu';
+
+DROP TABLE t2;
+DROP TABLE t1;
diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc
index eaf52a9ca09..ac6220014d1 100644
--- a/sql/ha_innodb.cc
+++ b/sql/ha_innodb.cc
@@ -465,6 +465,10 @@ convert_error_code_to_mysql(
 
     		return(HA_ERR_FOUND_DUPP_KEY);
 
+  	} else if (error == (int) DB_FOREIGN_DUPLICATE_KEY) {
+
+		return(HA_ERR_FOREIGN_DUPLICATE_KEY);
+
  	} else if (error == (int) DB_RECORD_NOT_FOUND) {
 
     		return(HA_ERR_NO_ACTIVE_RECORD);
diff --git a/sql/handler.cc b/sql/handler.cc
index b40a40684fe..dbd717b5498 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -358,6 +358,7 @@ static int ha_init_errors(void)
   SETMSG(HA_ERR_TABLE_EXIST,            ER(ER_TABLE_EXISTS_ERROR));
   SETMSG(HA_ERR_NO_CONNECTION,          "Could not connect to storage engine");
   SETMSG(HA_ERR_TABLE_DEF_CHANGED,      ER(ER_TABLE_DEF_CHANGED));
+  SETMSG(HA_ERR_FOREIGN_DUPLICATE_KEY,  "FK constraint would lead to duplicate key");
 
   /* Register the error messages for use with my_error(). */
   return my_error_register(errmsgs, HA_ERR_FIRST, HA_ERR_LAST);
@@ -1868,6 +1869,29 @@ void handler::print_error(int error, myf errflag)
     textno=ER_DUP_KEY;
     break;
   }
+  case HA_ERR_FOREIGN_DUPLICATE_KEY:
+  {
+    uint key_nr= get_dup_key(error);
+    if ((int) key_nr >= 0)
+    {
+      /* Write the key in the error message */
+      char key[MAX_KEY_LENGTH];
+      String str(key,sizeof(key),system_charset_info);
+      /* Table is opened and defined at this point */
+      key_unpack(&str,table,(uint) key_nr);
+      uint max_length= MYSQL_ERRMSG_SIZE-(uint) strlen(ER(ER_FOREIGN_DUPLICATE_KEY));
+      if (str.length() >= max_length)
+      {
+        str.length(max_length-4);
+        str.append(STRING_WITH_LEN("..."));
+      }
+      my_error(ER_FOREIGN_DUPLICATE_KEY, MYF(0), table_share->table_name.str,
+        str.c_ptr(), key_nr+1);
+      DBUG_VOID_RETURN;
+    }
+    textno= ER_DUP_KEY;
+    break;
+  }
   case HA_ERR_NULL_IN_SPATIAL:
     textno= ER_UNKNOWN_ERROR;
     break;
@@ -2003,8 +2027,9 @@ uint handler::get_dup_key(int error)
 {
   DBUG_ENTER("handler::get_dup_key");
   table->file->errkey  = (uint) -1;
-  if (error == HA_ERR_FOUND_DUPP_KEY || error == HA_ERR_FOUND_DUPP_UNIQUE ||
-      error == HA_ERR_NULL_IN_SPATIAL || error == HA_ERR_DROP_INDEX_FK)
+  if (error == HA_ERR_FOUND_DUPP_KEY || error == HA_ERR_FOREIGN_DUPLICATE_KEY ||
+      error == HA_ERR_FOUND_DUPP_UNIQUE || error == HA_ERR_NULL_IN_SPATIAL ||
+      error == HA_ERR_DROP_INDEX_FK)
     info(HA_STATUS_ERRKEY | HA_STATUS_NO_LOCK);
   DBUG_RETURN(table->file->errkey);
 }
diff --git a/sql/share/errmsg.txt b/sql/share/errmsg.txt
index 1099b410290..a1c7ca652fd 100644
--- a/sql/share/errmsg.txt
+++ b/sql/share/errmsg.txt
@@ -5800,3 +5800,5 @@ ER_CANT_READ_LOCK_LOG_TABLE
         eng "You can't use usual read lock with log tables. Try READ LOCAL instead."
 ER_SP_WRONG_NAME 42000
 	eng "Incorrect routine name '%-.64s'"
+ER_FOREIGN_DUPLICATE_KEY 23000 S1009
+	eng "Upholding foreign key constraints for table '%.64s', entry '%-.64s', key %d would lead to a duplicate entry"
diff --git a/storage/innobase/include/db0err.h b/storage/innobase/include/db0err.h
index de5ac44e73f..7f75e7e10a6 100644
--- a/storage/innobase/include/db0err.h
+++ b/storage/innobase/include/db0err.h
@@ -57,6 +57,10 @@ Created 5/24/1996 Heikki Tuuri
 					buffer pool (for big transactions,
 					InnoDB stores the lock structs in the
 					buffer pool) */
+#define DB_FOREIGN_DUPLICATE_KEY 46	/* foreign key constraints
+					activated by the operation would
+					lead to a duplicate key in some
+					table */
 
 /* The following are partial failure codes */
 #define DB_FAIL 		1000
diff --git a/storage/innobase/row/row0ins.c b/storage/innobase/row/row0ins.c
index 5e833372299..128b46f9aa4 100644
--- a/storage/innobase/row/row0ins.c
+++ b/storage/innobase/row/row0ins.c
@@ -1376,6 +1376,21 @@ run_again:
 						thr, foreign, &pcur, entry,
 									&mtr);
 					if (err != DB_SUCCESS) {
+						/* Since reporting a plain
+						"duplicate key" error
+						message to the user in
+						cases where a long CASCADE
+						operation would lead to a
+						duplicate key in some
+						other table is very
+						confusing, map duplicate
+						key errors resulting from
+						FK constraints to a
+						separate error code. */
+				    
+						if (err == DB_DUPLICATE_KEY) {
+						    err = DB_FOREIGN_DUPLICATE_KEY;
+						}
 
 						break;
 					}
diff --git a/storage/innobase/row/row0mysql.c b/storage/innobase/row/row0mysql.c
index 86d9ecf9c54..a16ffc5aa41 100644
--- a/storage/innobase/row/row0mysql.c
+++ b/storage/innobase/row/row0mysql.c
@@ -473,8 +473,9 @@ handle_new_error:
 	ut_a(err != DB_SUCCESS);
 	
 	trx->error_state = DB_SUCCESS;
-
-	if (err == DB_DUPLICATE_KEY) {
+	
+	if ((err == DB_DUPLICATE_KEY)
+		|| (err == DB_FOREIGN_DUPLICATE_KEY)) {
            	if (savept) {
 			/* Roll back the latest, possibly incomplete
 			insertion or update */