php - SQL Foreign Key General Error 1215 when creating migrations -

i built 2 migrations:

public function up() {     schema::create('incidents', function (blueprint $table) {         $table->increments('id');         $table->string('user_id');         $table->integer('incident_type_id')->unsigned();         $table->string('type');         $table->string('incident_reference');         $table->integer('incident_id');         $table->date('date');         $table->time('time');         $table->string('location');         $table->string('street');         $table->string('city');         $table->double('latitude', 10, 6);         $table->double('longitude', 10, 6);         $table->smallinteger('incident_archived')->default(0);         $table->timestamps();     }); } 

and other one:

public function up() {     schema::create('responders', function (blueprint $table) {         $table->increments('id');         $table->string('user_id');         $table->string('responder_id');         $table->integer('incident_id');         $table->foreign('incident_id')->references('incident_id')->on('incidents');         $table->double('last_lat', 10, 6);         $table->double('last_lng', 10, 6);         $table->timestamps();     }); } 

now want use incident_id foreign key incidents table. error: cannot add foreign key constraint. first thought order of migrations causes trouble, responder table created before incident table. not case. why blocked using incident_id foreign key then?

thank you