diff --git a/src/utils/videoFit.test.ts b/src/utils/videoFit.test.ts
index 9390e8d4..5068526b 100644
--- a/src/utils/videoFit.test.ts
+++ b/src/utils/videoFit.test.ts
@@ -116,6 +116,18 @@ test.each([
     tileSize: VIDEO_480_L,
     expected: "contain",
   },
+  {
+    // Should default to cover if the initial size is 0:0.
+    // Or else it will cause a flash of "contain" mode until the real size is loaded, which can be jarring.
+    videoSize: VIDEO_480_L,
+    tileSize: { width: 0, height: 0 },
+    expected: "cover",
+  },
+  {
+    videoSize: { width: 0, height: 0 },
+    tileSize: VIDEO_480_L,
+    expected: "cover",
+  },
 ])(
   "videoFit$ returns $expected when videoSize is $videoSize and tileSize is $tileSize",
   ({ videoSize, tileSize, expected }) => {
diff --git a/src/utils/videoFit.ts b/src/utils/videoFit.ts
index c7b18f03..5f2cc2ce 100644
--- a/src/utils/videoFit.ts
+++ b/src/utils/videoFit.ts
@@ -36,6 +36,15 @@ export function videoFit$(
         // This is a reasonable default as it will ensure the video fills the tile, even if it means cropping.
         return "cover";
       }
+      if (
+        videoSize.width === 0 ||
+        videoSize.height === 0 ||
+        tileSize.width === 0 ||
+        tileSize.height === 0
+      ) {
+        // If we have invalid sizes (e.g. width or height is 0), default to cover to avoid black bars.
+        return "cover";
+      }
       const videoAspectRatio = videoSize.width / videoSize.height;
       const tileAspectRatio = tileSize.width / tileSize.height;