diff --git a/www/manager6/Utils.js b/www/manager6/Utils.js
index 4041c010..8631a67c 100644
--- a/www/manager6/Utils.js
+++ b/www/manager6/Utils.js
@@ -1757,6 +1757,52 @@ Ext.define('PVE.Utils', {
 
 	return true;
     },
+
+    sortByPreviousUsage: function(vmconfig, controllerList) {
+	if (!controllerList) {
+	    controllerList = ['ide', 'virtio', 'scsi', 'sata'];
+	}
+	let usedControllers = {};
+	for (const type of Object.keys(PVE.Utils.diskControllerMaxIDs)) {
+	    usedControllers[type] = 0;
+	}
+
+	for (const property of Object.keys(vmconfig)) {
+	    if (property.match(PVE.Utils.bus_match) && !vmconfig[property].match(/media=cdrom/)) {
+		const foundController = property.match(PVE.Utils.bus_match)[1];
+		usedControllers[foundController]++;
+	    }
+	}
+
+	let sortPriority = PVE.qemu.OSDefaults.getDefaults(vmconfig.ostype).busPriority;
+
+	let sortedList = Ext.clone(controllerList);
+	sortedList.sort(function(a, b) {
+	    if (usedControllers[b] === usedControllers[a]) {
+		return sortPriority[b] - sortPriority[a];
+	    }
+	    return usedControllers[b] - usedControllers[a];
+	});
+
+	return sortedList;
+    },
+
+    nextFreeDisk: function(controllers, config) {
+	for (const controller of controllers) {
+	    for (let i = 0; i < PVE.Utils.diskControllerMaxIDs[controller]; i++) {
+		let confid = controller + i.toString();
+		if (!Ext.isDefined(config[confid])) {
+		    return {
+			controller,
+			id: i,
+			confid,
+		    };
+		}
+	    }
+	}
+
+	return undefined;
+    },
 },
 
     singleton: true,
diff --git a/www/manager6/form/ControllerSelector.js b/www/manager6/form/ControllerSelector.js
index 27c06169..fcf625a1 100644
--- a/www/manager6/form/ControllerSelector.js
+++ b/www/manager6/form/ControllerSelector.js
@@ -6,44 +6,15 @@ Ext.define('PVE.form.ControllerSelector', {
 
     vmconfig: {}, // used to check for existing devices
 
-    sortByPreviousUsage: function(vmconfig, controllerList) {
-	let usedControllers = {};
-	for (const type of Object.keys(PVE.Utils.diskControllerMaxIDs)) {
-	    usedControllers[type] = 0;
-	}
-
-	for (const property of Object.keys(vmconfig)) {
-	    if (property.match(PVE.Utils.bus_match) && !vmconfig[property].match(/media=cdrom/)) {
-		const foundController = property.match(PVE.Utils.bus_match)[1];
-		usedControllers[foundController]++;
-	    }
-	}
-
-	let sortPriority = PVE.qemu.OSDefaults.getDefaults(vmconfig.ostype).busPriority;
-
-	let sortedList = Ext.clone(controllerList);
-	sortedList.sort(function(a, b) {
-	    if (usedControllers[b] === usedControllers[a]) {
-		return sortPriority[b] - sortPriority[a];
-	    }
-	    return usedControllers[b] - usedControllers[a];
-	});
-
-	return sortedList;
-    },
-
     setToFree: function(controllers, busField, deviceIDField) {
 	let me = this;
-	for (const controller of controllers) {
-	    busField.setValue(controller);
-	    for (let i = 0; i < PVE.Utils.diskControllerMaxIDs[controller]; i++) {
-		let confid = controller + i.toString();
-		if (!Ext.isDefined(me.vmconfig[confid])) {
-		    deviceIDField.setValue(i);
-		    return;
-		}
-	    }
+	let freeId = PVE.Utils.nextFreeDisk(controllers, me.vmconfig);
+
+	if (freeId !== undefined) {
+	    busField.setValue(freeId.controller);
+	    deviceIDField.setValue(freeId.id);
 	}
+
     },
 
     setVMConfig: function(vmconfig, autoSelect) {
@@ -54,7 +25,7 @@ Ext.define('PVE.form.ControllerSelector', {
 	let bussel = me.down('field[name=controller]');
 	let deviceid = me.down('field[name=deviceid]');
 
-	let clist = ['ide', 'virtio', 'scsi', 'sata'];
+	let clist;
 	if (autoSelect === 'cdrom') {
 	    if (!Ext.isDefined(me.vmconfig.ide2)) {
 		bussel.setValue('ide');
@@ -64,7 +35,7 @@ Ext.define('PVE.form.ControllerSelector', {
 	    clist = ['ide', 'scsi', 'sata'];
 	} else {
 	    // in most cases we want to add a disk to the same controller we previously used
-	    clist = me.sortByPreviousUsage(me.vmconfig, clist);
+	    clist = PVE.Utils.sortByPreviousUsage(me.vmconfig);
 	}
 
 	me.setToFree(clist, bussel, deviceid);