diff --git a/css-element-queries.d.ts b/css-element-queries.d.ts
index 97ee144..3fe0706 100644
--- a/css-element-queries.d.ts
+++ b/css-element-queries.d.ts
@@ -1,2 +1,2 @@
-export { ResizeSensor, ResizeSensorCallback } from "./src/ResizeSensor";
+export { ResizeSensor, ResizeSensorCallback, Size } from "./src/ResizeSensor";
 export { ElementQueries } from './src/ElementQueries';
\ No newline at end of file
diff --git a/src/ResizeSensor.d.ts b/src/ResizeSensor.d.ts
index ad6c412..3fba8c6 100644
--- a/src/ResizeSensor.d.ts
+++ b/src/ResizeSensor.d.ts
@@ -1,4 +1,9 @@
-export declare type ResizeSensorCallback = (size: { width: number; height: number; }) => void;
+export declare interface Size {
+    width: number;
+    height: number;
+}
+
+export declare type ResizeSensorCallback = (size: Size) => void;
 
 export declare class ResizeSensor {
     /**
diff --git a/src/ResizeSensor.js b/src/ResizeSensor.js
index 12985d0..9a25503 100755
--- a/src/ResizeSensor.js
+++ b/src/ResizeSensor.js
@@ -305,7 +305,7 @@
 
         this.detach = function(ev) {
             // clean up the unfinished animation frame to prevent a potential endless requestAnimationFrame of reset
-            if (!lastAnimationFrameForInvisibleCheck) {
+            if (lastAnimationFrameForInvisibleCheck) {
                 cancelAnimationFrame(lastAnimationFrameForInvisibleCheck);
                 lastAnimationFrameForInvisibleCheck = 0;
             }
@@ -313,13 +313,19 @@
         };
 
         this.reset = function() {
-            element.resizeSensor.resetSensor();
+            //To prevent invoking element.resizeSensor.resetSensor if it's undefined
+            if (element.resizeSensor.resetSensor) {
+                element.resizeSensor.resetSensor();
+            }
         };
     };
 
     ResizeSensor.reset = function(element) {
         forEachElement(element, function(elem){
-            elem.resizeSensor.resetSensor();
+            //To prevent invoking element.resizeSensor.resetSensor if it's undefined
+            if (element.resizeSensor.resetSensor) {
+                elem.resizeSensor.resetSensor();
+            }
         });
     };