diff --git a/src/main/kotlin/application/controller/MenuBarController.kt b/src/main/kotlin/application/controller/MenuBarController.kt
index 84dfe7d..6d94861 100644
--- a/src/main/kotlin/application/controller/MenuBarController.kt
+++ b/src/main/kotlin/application/controller/MenuBarController.kt
@@ -7,6 +7,7 @@ import application.model.observableVessel
 import javafx.event.EventHandler
 import javafx.fxml.FXML
 import javafx.fxml.Initializable
+import javafx.scene.control.Alert
 import javafx.scene.control.CheckMenuItem
 import javafx.scene.control.MenuBar
 import javafx.scene.control.MenuItem
@@ -52,10 +53,17 @@ class MenuBarController : Initializable {
             val window = menuBar.scene.window
             val file = fileChooser.showOpenDialog(window)
             try {
+                if (file.extension != "csv") {
+                    val alert = Alert(Alert.AlertType.WARNING)
+                    alert.title = "Warning Alert"
+                    alert.headerText = "Wrong file format."
+                    alert.contentText = "Please choose à .csv file."
+                    alert.showAndWait()
+                }
                 val vessels = createVesselCollection(file)
                 observableVessel.vessels.clear()
                 observableVessel.vessels = vessels
-            } catch (ignore: IllegalStateException){
+            } catch (ignore: IllegalStateException) {
 
             }
         }
diff --git a/src/main/kotlin/map/MapDisplayer.kt b/src/main/kotlin/map/MapDisplayer.kt
index 859acc9..e1be20b 100644
--- a/src/main/kotlin/map/MapDisplayer.kt
+++ b/src/main/kotlin/map/MapDisplayer.kt
@@ -88,7 +88,6 @@ fun displayHeatMapOnMap(map: LeafletMapView) {
             map.execScript("heatLayer.addLatLng([${message.latitude}, ${message.longitude}]);")
         }
     }
-
 }
 
 fun displayHeatMapOnMap(map: LeafletMapView, selectedMMSI: Int) {