diff --git a/components/lib/dialog/BaseDialog.vue b/components/lib/dialog/BaseDialog.vue
index 9ddf7a929..4e30a72d4 100644
--- a/components/lib/dialog/BaseDialog.vue
+++ b/components/lib/dialog/BaseDialog.vue
@@ -160,13 +160,18 @@ const inlineStyles = {
 };
 
 const classes = {
-    mask: ({ props, instance }) => [
-        'p-dialog-mask',
-        {
-            'p-component-overlay p-component-overlay-enter': props.modal
-        },
-        instance.getPositionClass()
-    ],
+    mask: ({ props }) => {
+        const positions = ['left', 'right', 'top', 'topleft', 'topright', 'bottom', 'bottomleft', 'bottomright'];
+        const pos = positions.find((item) => item === props.position);
+
+        return [
+            'p-dialog-mask',
+            {
+                'p-component-overlay p-component-overlay-enter': props.modal
+            },
+            pos ? `p-dialog-${pos}` : ''
+        ];
+    },
     root: ({ props, instance }) => [
         'p-dialog p-component',
         {
diff --git a/components/lib/dialog/Dialog.vue b/components/lib/dialog/Dialog.vue
index 22b6b45f6..5346cd7ce 100755
--- a/components/lib/dialog/Dialog.vue
+++ b/components/lib/dialog/Dialog.vue
@@ -222,12 +222,6 @@ export default {
                 this.documentKeydownListener = null;
             }
         },
-        getPositionClass() {
-            const positions = ['left', 'right', 'top', 'topleft', 'topright', 'bottom', 'bottomleft', 'bottomright'];
-            const pos = positions.find((item) => item === this.position);
-
-            return pos ? `p-dialog-${pos}` : '';
-        },
         containerRef(el) {
             this.container = el;
         },