diff --git a/types/quill/index.d.ts b/types/quill/index.d.ts
index 650408c67c..73a877815f 100644
--- a/types/quill/index.d.ts
+++ b/types/quill/index.d.ts
@@ -69,9 +69,9 @@ declare namespace Quill {
         concat(other: DeltaStatic): DeltaStatic;
         diff(other: DeltaStatic, index?: number) : DeltaStatic;
         eachLine(predicate: (line: DeltaStatic, attributes: StringMap, idx: number) => any, newline?: string) : DeltaStatic;
-        transform(index: number) : DeltaStatic;
+        transform(index: number) : number;
         transform(other: DeltaStatic, priority: boolean) : DeltaStatic;
-        transformPosition(index: number) : DeltaStatic;
+        transformPosition(index: number) : number;
     }
 
     export interface RangeStatic {
diff --git a/types/quill/quill-tests.ts b/types/quill/quill-tests.ts
index fe2af00afc..f45781a685 100644
--- a/types/quill/quill-tests.ts
+++ b/types/quill/quill-tests.ts
@@ -324,13 +324,14 @@ function test_DeltaTransform() {
     var a = new Delta().insert('a');
     var b = new Delta().insert('b').retain(5).insert('c');
 
-    a.transform(b, true);  // new Delta().retain(1).insert('b').retain(5).insert('c');
-    a.transform(b, false); // new Delta().insert('b').retain(6).insert('c');
-    a.transform(5);
+    var d1: Quill.DeltaStatic = a.transform(b, true);  // new Delta().retain(1).insert('b').retain(5).insert('c');
+    var d2: Quill.DeltaStatic = a.transform(b, false); // new Delta().insert('b').retain(6).insert('c');
+    var n1: number = a.transform(5);
+
 }
 
 function test_DeltatransformPosition() {
     var delta = new Delta().retain(5).insert('a');
-    delta.transformPosition(4); // 4
-    delta.transformPosition(5); // 6
+    var n1: number = delta.transformPosition(4); // 4
+    var n2: number = delta.transformPosition(5); // 6
 }