diff --git a/index.js b/index.js
index e455c0d..dc2b9b6 100644
--- a/index.js
+++ b/index.js
@@ -35,6 +35,10 @@ Create a TransformStream that passes only the first `count` chunks.
 @returns {TransformStream} A TransformStream that limits chunks.
 */
 export function takeStream(count) {
+  if (!Number.isInteger(count) || count < 0) {
+    throw new TypeError("Expected count to be a non-negative integer");
+  }
+
   let taken = 0;
   return new TransformStream({
     transform(chunk, controller) {
@@ -57,6 +61,10 @@ Create a TransformStream that collects chunks into arrays of a given size.
 @returns {TransformStream} A TransformStream that batches chunks.
 */
 export function batchStream(size) {
+  if (!Number.isInteger(size) || size <= 0) {
+    throw new TypeError("Expected size to be a positive integer");
+  }
+
   let buffer = [];
   return new TransformStream({
     flush(controller) {
diff --git a/test.js b/test.js
index 890f046..b49b9f2 100644
--- a/test.js
+++ b/test.js
@@ -129,6 +129,14 @@ test("takeStream returns empty for count 0", async (t) => {
   t.deepEqual(result, []);
 });
 
+test("takeStream rejects invalid counts", (t) => {
+  t.throws(() => takeStream(-1), {
+    instanceOf: TypeError,
+    message: "Expected count to be a non-negative integer",
+  });
+  t.throws(() => takeStream(1.5), { instanceOf: TypeError });
+});
+
 test("takeStream takes exactly 1", async (t) => {
   const result = await collectStream(
     createReadable([10, 20, 30]).pipeThrough(takeStream(1))
@@ -162,6 +170,14 @@ test("batchStream with size 1 wraps each chunk", async (t) => {
   t.deepEqual(result, [[1], [2], [3]]);
 });
 
+test("batchStream rejects invalid sizes", (t) => {
+  t.throws(() => batchStream(0), {
+    instanceOf: TypeError,
+    message: "Expected size to be a positive integer",
+  });
+  t.throws(() => batchStream(1.5), { instanceOf: TypeError });
+});
+
 test("batchStream handles empty stream", async (t) => {
   const result = await collectStream(
     createReadable([]).pipeThrough(batchStream(3))