diff --git a/mysql-test/main/long_unique_bugs.result b/mysql-test/main/long_unique_bugs.result
index 81482e68417..b01a0dd2256 100644
--- a/mysql-test/main/long_unique_bugs.result
+++ b/mysql-test/main/long_unique_bugs.result
@@ -674,6 +674,25 @@ SELECT * FROM t1;
 a	b	c
 3	2	2
 DROP TABLE t1;
+# MDEV-30046 wrong row targeted with "insert ... on duplicate" and
+# "replace", leading to data corruption
+create table t (s blob, n int, unique (s)) engine=innodb;
+insert into t values ('Hrecvx_0004ln-00',1), ('Hrecvx_0004mm-00',1);
+replace into t values ('Hrecvx_0004mm-00',2);
+select * from t;
+s	n
+Hrecvx_0004ln-00	1
+Hrecvx_0004mm-00	2
+drop table t;
+create table t (s blob, n int, unique (s)) engine=innodb;
+insert into t values ('Hrecvx_0004ln-00',1), ('Hrecvx_0004mm-00',1);
+insert into t values ('Hrecvx_0004mm-00',2)
+on duplicate key update n = values (n);
+select * from t;
+s	n
+Hrecvx_0004ln-00	1
+Hrecvx_0004mm-00	2
+drop table t;
 #
 # End of 10.5 tests
 #
diff --git a/mysql-test/main/long_unique_bugs.test b/mysql-test/main/long_unique_bugs.test
index 2441dfa59e8..3c2ab4d70f5 100644
--- a/mysql-test/main/long_unique_bugs.test
+++ b/mysql-test/main/long_unique_bugs.test
@@ -655,6 +655,21 @@ REPLACE INTO t1 VALUES (3,2,2);
 SELECT * FROM t1;
 DROP TABLE t1;
 
+--echo # MDEV-30046 wrong row targeted with "insert ... on duplicate" and
+--echo # "replace", leading to data corruption
+--source include/have_innodb.inc
+create table t (s blob, n int, unique (s)) engine=innodb;
+insert into t values ('Hrecvx_0004ln-00',1), ('Hrecvx_0004mm-00',1);
+replace into t values ('Hrecvx_0004mm-00',2);
+select * from t;
+drop table t;
+
+create table t (s blob, n int, unique (s)) engine=innodb;
+insert into t values ('Hrecvx_0004ln-00',1), ('Hrecvx_0004mm-00',1);
+insert into t values ('Hrecvx_0004mm-00',2)
+    on duplicate key update n = values (n);
+select * from t;
+drop table t;
 --echo #
 --echo # End of 10.5 tests
 --echo #
diff --git a/sql/handler.cc b/sql/handler.cc
index 7f5cb343824..e2fe80a260d 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -4569,6 +4569,12 @@ uint handler::get_dup_key(int error)
   DBUG_RETURN(errkey);
 }
 
+bool handler::has_dup_ref() const
+{
+  DBUG_ASSERT(lookup_errkey != (uint)-1 || errkey != (uint)-1);
+  return ha_table_flags() & HA_DUPLICATE_POS || lookup_errkey != (uint)-1;
+}
+
 
 /**
   Delete all files with extension from bas_ext().
@@ -6996,11 +7002,8 @@ exit:
   if (error == HA_ERR_FOUND_DUPP_KEY)
   {
     table->file->lookup_errkey= key_no;
-    if (ha_table_flags() & HA_DUPLICATE_POS)
-    {
-      lookup_handler->position(table->record[0]);
-      memcpy(table->file->dup_ref, lookup_handler->ref, ref_length);
-    }
+    lookup_handler->position(table->record[0]);
+    memcpy(table->file->dup_ref, lookup_handler->ref, ref_length);
   }
   restore_record(table, file->lookup_buffer);
   table->restore_blob_values(blob_storage);
diff --git a/sql/handler.h b/sql/handler.h
index 0b0ffe6be27..f858553c7b7 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -3464,6 +3464,7 @@ public:
   virtual void print_error(int error, myf errflag);
   virtual bool get_error_message(int error, String *buf);
   uint get_dup_key(int error);
+  bool has_dup_ref() const;
   /**
     Retrieves the names of the table and the key for which there was a
     duplicate entry in the case of HA_ERR_FOREIGN_DUPLICATE_KEY.
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index b3314e075f0..1e0a6a75338 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -1884,11 +1884,28 @@ int write_record(THD *thd, TABLE *table, COPY_INFO *info, select_result *sink)
       if (info->handle_duplicates == DUP_REPLACE && table->next_number_field &&
           key_nr == table->s->next_number_index && insert_id_for_cur_row > 0)
 	goto err;
-      if (table->file->ha_table_flags() & HA_DUPLICATE_POS)
+      if (table->file->has_dup_ref())
       {
+        /*
+          If engine doesn't support HA_DUPLICATE_POS, the handler may init to
+          INDEX, but dup_ref could also be set by lookup_handled (and then,
+          lookup_errkey is set, f.ex. long unique duplicate).
+
+          In such case, handler would stay uninitialized, so do it here.
+         */
+        bool init_lookup_handler= table->file->lookup_errkey != (uint)-1 &&
+                                  table->file->inited == handler::NONE;
+        if (init_lookup_handler && table->file->ha_rnd_init_with_error(false))
+          goto err;
+
         DBUG_ASSERT(table->file->inited == handler::RND);
-	if (table->file->ha_rnd_pos(table->record[1],table->file->dup_ref))
-	  goto err;
+	int rnd_pos_err= table->file->ha_rnd_pos(table->record[1],
+                                                 table->file->dup_ref);
+
+        if (init_lookup_handler)
+          table->file->ha_rnd_end();
+        if (rnd_pos_err)
+          goto err;
       }
       else
       {