diff --git a/lib/filepicker.ts b/lib/filepicker.ts
index c5ec1450..e4f9ae33 100644
--- a/lib/filepicker.ts
+++ b/lib/filepicker.ts
@@ -1,131 +1,171 @@
 /// <reference types="@nextcloud/typings" />
 
-declare const OC: Nextcloud.v25.OC | Nextcloud.v26.OC | Nextcloud.v27.OC;
-
 export enum FilePickerType {
-    Choose = 1,
-    Move = 2,
-    Copy = 3,
-    CopyMove = 4,
-    Custom = 5,
+	Choose = 1,
+	Move = 2,
+	Copy = 3,
+	CopyMove = 4,
+	Custom = 5,
+}
+
+export interface FilePickerButton {
+	text: string
+	type?: 'primary' | 'secondary'
+	/** Passed on the callback as second argument */
+	id: number
 }
 
 export class FilePicker {
-    private title: string
-    private multiSelect: boolean
-    private mimeTypeFiler: string[]
-    private modal: boolean
-    private type: FilePickerType
-    private directoriesAllowed: boolean
-    private path?: string
-    private filter?: Nextcloud.v24.FilePickerFilter
-
-    public constructor(title: string,
-        multiSelect: boolean,
-        mimeTypeFilter: string[],
-        modal: boolean,
-        type: FilePickerType,
-        directoriesAllowed: boolean,
-        path?: string,
-        filter?: Nextcloud.v24.FilePickerFilter) {
-        this.title = title
-        this.multiSelect = multiSelect
-        this.mimeTypeFiler = mimeTypeFilter
-        this.modal = modal
-        this.type = type
-        this.directoriesAllowed = directoriesAllowed
-        this.path = path
-        this.filter = filter
-    }
-
-    public pick(): Promise<string> {
-        return new Promise((res, rej) => {
-            OC.dialogs.filepicker(
-                this.title,
-                res,
-                this.multiSelect,
-                this.mimeTypeFiler,
-                this.modal,
-                this.type,
-                this.path,
-                {
-                    allowDirectoryChooser: this.directoriesAllowed,
-                    filter: this.filter,
-                },
-            )
-        })
-    }
+
+	private title: string
+	private multiSelect: boolean
+	private mimeTypeFiler: string[]
+	private modal: boolean
+	private type: FilePickerType
+	private directoriesAllowed: boolean
+	private buttons?: FilePickerButton[]
+	private path?: string
+	private filter?: Nextcloud.v24.FilePickerFilter
+
+	public constructor(title: string,
+		multiSelect: boolean,
+		mimeTypeFilter: string[],
+		modal: boolean,
+		type: FilePickerType,
+		directoriesAllowed: boolean,
+		path?: string,
+		filter?: Nextcloud.v24.FilePickerFilter,
+		buttons?: FilePickerButton[]) {
+		this.title = title
+		this.multiSelect = multiSelect
+		this.mimeTypeFiler = mimeTypeFilter
+		this.modal = modal
+		this.type = type
+		this.directoriesAllowed = directoriesAllowed
+		this.path = path
+		this.filter = filter
+		this.buttons = buttons
+	}
+
+	public async pick(): Promise<[string|string[], FilePickerType]> {
+		// Async import for module splitting (treeshaking)
+		const filepicker = (await import('./legacy')).filepicker
+
+		return new Promise((resolve) => {
+			const buttons = this.buttons?.map(button => ({
+				defaultButton: button.type === 'primary',
+				label: button.text,
+				type: button.id,
+			}))
+
+			filepicker(
+				this.title,
+				(path: string | string[], type: FilePickerType) => resolve([path, type]),
+				this.multiSelect,
+				this.mimeTypeFiler,
+				this.modal,
+				this.type,
+				this.path,
+				{
+					allowDirectoryChooser: this.directoriesAllowed,
+					filter: this.filter,
+					buttons,
+				},
+			)
+		})
+	}
+
 }
 
 export class FilePickerBuilder {
-    private title: string
-    private multiSelect: boolean = false
-    private mimeTypeFiler: string[] = []
-    private modal: boolean = true
-    private type: FilePickerType = FilePickerType.Choose
-    private directoriesAllowed: boolean = false
-    private path?: string
-    private filter?: Nextcloud.v24.FilePickerFilter
-
-    public constructor(title: string) {
-        this.title = title
-    }
-
-    public setMultiSelect(ms: boolean): FilePickerBuilder {
-        this.multiSelect = ms
-        return this
-    }
-
-    public addMimeTypeFilter(filter: string): FilePickerBuilder {
-        this.mimeTypeFiler.push(filter)
-        return this
-    }
-
-    public setMimeTypeFilter(filter: string[]): FilePickerBuilder {
-        this.mimeTypeFiler = filter
-        return this
-    }
-
-    public setModal(modal: boolean): FilePickerBuilder {
-        this.modal = modal
-        return this
-    }
-
-    public setType(type: FilePickerType): FilePickerBuilder {
-        this.type = type
-        return this
-    }
-
-    public allowDirectories(allow: boolean = true): FilePickerBuilder {
-        this.directoriesAllowed = allow
-        return this
-    }
-
-    public startAt(path: string): FilePickerBuilder {
-        this.path = path
-        return this
-    }
-
-    public setFilter(filter: Nextcloud.v24.FilePickerFilter): FilePickerBuilder {
-        this.filter = filter
-        return this
-    }
-
-    public build(): FilePicker {
-        return new FilePicker(
-            this.title,
-            this.multiSelect,
-            this.mimeTypeFiler,
-            this.modal,
-            this.type,
-            this.directoriesAllowed,
-            this.path,
-            this.filter,
-        )
-    }
+
+	private title: string
+	private multiSelect = false
+	private mimeTypeFiler: string[] = []
+	private modal = true
+	private type: FilePickerType = FilePickerType.Choose
+	private directoriesAllowed = false
+	private path?: string
+	private filter?: Nextcloud.v24.FilePickerFilter
+	private buttons: FilePickerButton[] = []
+
+	public constructor(title: string) {
+		this.title = title
+	}
+
+	public setMultiSelect(ms: boolean): FilePickerBuilder {
+		this.multiSelect = ms
+		return this
+	}
+
+	public addMimeTypeFilter(filter: string): FilePickerBuilder {
+		this.mimeTypeFiler.push(filter)
+		return this
+	}
+
+	public setMimeTypeFilter(filter: string[]): FilePickerBuilder {
+		this.mimeTypeFiler = filter
+		return this
+	}
+
+	public addButton(button: FilePickerButton): FilePickerBuilder {
+		this.buttons.push(button)
+		return this
+	}
+
+	/**
+	 * @param modal no function
+	 * @deprecated Does not have any effect as the dialog is always modal
+	 */
+	public setModal(modal: boolean): FilePickerBuilder {
+		this.modal = modal
+		return this
+	}
+
+	public setType(type: FilePickerType): FilePickerBuilder {
+		this.type = type
+		return this
+	}
+
+	public allowDirectories(allow = true): FilePickerBuilder {
+		this.directoriesAllowed = allow
+		return this
+	}
+
+	public startAt(path: string): FilePickerBuilder {
+		this.path = path
+		return this
+	}
+
+	public setFilter(filter: Nextcloud.v24.FilePickerFilter): FilePickerBuilder {
+		this.filter = filter
+		return this
+	}
+
+	public build(): FilePicker {
+		if (this.buttons && this.type !== FilePickerType.Custom) {
+			console.error('FilePickerBuilder: When adding custom buttons the `type` must be set to `FilePickerType.Custom`.')
+		}
+
+		return new FilePicker(
+			this.title,
+			this.multiSelect,
+			this.mimeTypeFiler,
+			this.modal,
+			this.type,
+			this.directoriesAllowed,
+			this.path,
+			this.filter,
+			this.buttons,
+		)
+	}
 
 }
 
+/**
+ *
+ * @param title Title of the file picker
+ */
 export function getFilePickerBuilder(title: string): FilePickerBuilder {
-    return new FilePickerBuilder(title)
+	return new FilePickerBuilder(title)
 }