diff --git a/src/components/GridTaskBlock.tsx b/src/components/GridTaskBlock.tsx
index 42f116c..f459a56 100644
--- a/src/components/GridTaskBlock.tsx
+++ b/src/components/GridTaskBlock.tsx
@@ -111,16 +111,18 @@ export function GridTaskBlock({
     const pixelsPerMinute = getSlotHeight(cellDuration) / cellDuration;
 
     useEffect(() => {
-        const onResizeMove = (e: MouseEvent) => {
+        if (!task.startTime) return;
+
+        const handleResizeMove = (e: MouseEvent) => {
             if (!isResizing) return;
             const deltaY = e.clientY - resizeStartY.current;
             let newHeight = resizeStartHeight.current + deltaY;
-            const minHeight = 15 * pixelsPerMinute; // min 15 mins
+            const minHeight = 15 * pixelsPerMinute;
             if (newHeight < minHeight) newHeight = minHeight;
             setResizeHeight(newHeight);
         };
 
-        const onResizeEnd = () => {
+        const handleResizeEnd = () => {
             if (!isResizing) return;
             setIsResizing(false);
             document.body.style.cursor = "";
@@ -132,15 +134,15 @@ export function GridTaskBlock({
         };
 
         if (isResizing) {
-            window.addEventListener("mousemove", onResizeMove);
-            window.addEventListener("mouseup", onResizeEnd);
+            window.addEventListener("mousemove", handleResizeMove);
+            window.addEventListener("mouseup", handleResizeEnd);
         }
 
         return () => {
-            window.removeEventListener("mousemove", onResizeMove);
-            window.removeEventListener("mouseup", onResizeEnd);
+            window.removeEventListener("mousemove", handleResizeMove);
+            window.removeEventListener("mouseup", handleResizeEnd);
         };
-    }, [isResizing, resizeHeight, pixelsPerMinute, task.id, updateTaskDuration]);
+    }, [isResizing, resizeHeight, pixelsPerMinute, task.id, updateTaskDuration, task.startTime]);
 
     if (!task.startTime) return null;