diff --git a/src/matroska/matroska-muxer.ts b/src/matroska/matroska-muxer.ts
index 587aabd..9df5e1f 100644
--- a/src/matroska/matroska-muxer.ts
+++ b/src/matroska/matroska-muxer.ts
@@ -1332,8 +1332,6 @@ export class MatroskaMuxer extends Muxer {
 		this.ebmlWriter.writeEBML(this.cues);
 
 		if (!this.format._options.appendOnly) {
-			const endPos = this.writer.getPos();
-
 			// Write the Segment size
 			const segmentSize = this.writer.getPos() - this.segmentDataOffset;
 			this.writer.seek(this.ebmlWriter.offsets.get(this.segment!)! + 4);
@@ -1352,8 +1350,6 @@ export class MatroskaMuxer extends Muxer {
 			this.writer.seek(this.ebmlWriter.offsets.get(this.seekHead)!);
 			this.maybeCreateSeekHead(true);
 			this.ebmlWriter.writeEBML(this.seekHead);
-
-			this.writer.seek(endPos);
 		}
 
 		release();
diff --git a/src/mp3/mp3-muxer.ts b/src/mp3/mp3-muxer.ts
index b36cc7f..17046cc 100644
--- a/src/mp3/mp3-muxer.ts
+++ b/src/mp3/mp3-muxer.ts
@@ -164,8 +164,6 @@ export class Mp3Muxer extends Muxer {
 			this.format._options.onXingFrame(data, start);
 		}
 
-		this.writer.seek(endPos);
-
 		release();
 	}
 }
diff --git a/src/target.ts b/src/target.ts
index c06e399..468d5d8 100644
--- a/src/target.ts
+++ b/src/target.ts
@@ -49,7 +49,7 @@ export abstract class Target {
 	onfinalized: (() => unknown) | null = null;
 
 	slice(offset: number) {
-		if (!Number.isInteger(offset) && offset < 0) {
+		if (!Number.isInteger(offset) || offset < 0) {
 			throw new TypeError('offset must be a non-negative integer.');
 		}
 
diff --git a/src/wave/wave-muxer.ts b/src/wave/wave-muxer.ts
index 5a5a77e..26319d7 100644
--- a/src/wave/wave-muxer.ts
+++ b/src/wave/wave-muxer.ts
@@ -369,8 +369,6 @@ export class WaveMuxer extends Muxer {
 			this.riffWriter.writeU32(this.dataSize);
 		}
 
-		this.writer.seek(endPos);
-
 		release();
 	}
 }
diff --git a/todo.txt b/todo.txt
index b8cbe0c..d08aba7 100644
--- a/todo.txt
+++ b/todo.txt
@@ -6,5 +6,4 @@ Also, why not just have the packet metadata on the packet? I think that would ma
 
 - Add an HLS "live mode". Challenge, where does bitrate come from?
 
-- fmp4 muxing (CMAF??)
-- ext-x-i-frames-only writing
\ No newline at end of file
+- fmp4 muxing (CMAF??)
\ No newline at end of file