diff --git a/src/codecs/decoders.ts b/src/codecs/decoders.ts
index 01a4ff36..0a739d51 100644
--- a/src/codecs/decoders.ts
+++ b/src/codecs/decoders.ts
@@ -26,7 +26,7 @@ export const decodersPromise: Promise<Decoder[]> = Promise.all(
 // values here.
 ).then(list => list.filter(item => !!item)) as any as Promise<Decoder[]>;
 
-export async function findDecodersByMimeType(mimeType: string): Promise<Decoder[]> {
+async function findDecodersByMimeType(mimeType: string): Promise<Decoder[]> {
   const decoders = await decodersPromise;
   return decoders.filter(decoder => decoder.canHandleMimeType(mimeType));
 }
diff --git a/src/lib/util.ts b/src/lib/util.ts
index fbd92e8d..fe67df9e 100644
--- a/src/lib/util.ts
+++ b/src/lib/util.ts
@@ -134,7 +134,7 @@ export async function sniffMimeType(blob: Blob): Promise<string> {
     Array.from(new Uint8Array(firstChunk))
       .map(v => String.fromCodePoint(v))
       .join('');
-  for (const [detector, mimeType] of magicNumberToMimeType.entries()) {
+  for (const [detector, mimeType] of magicNumberToMimeType) {
     if (detector.test(firstChunkString)) {
       return mimeType;
     }