diff --git a/src/images/staticWithMetadata.png b/src/images/staticWithMetadata.png
new file mode 100644
index 0000000..9b51945
Binary files /dev/null and b/src/images/staticWithMetadata.png differ
diff --git a/src/index.test.js b/src/index.test.js
index 21522db..6c1bdea 100644
--- a/src/index.test.js
+++ b/src/index.test.js
@@ -23,43 +23,63 @@ test('returns false on JPG', (t) => {
   t.false(check(dir + '/images/static.jpg'))
 })
 
+test('returns false on static PNG with `acTL` text in metadata', (t) => {
+  t.false(check(dir + '/images/staticWithMetadata.png'))
+})
+
 test('returns true when IDAT follows acTL', (t) => {
   t.true(
     isApng(
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // acTL
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: acTL
         0x61, 0x63, 0x54, 0x4c,
-        // IDAT
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: IDAT
         0x49, 0x44, 0x41, 0x54,
       ]),
     ),
   )
 })
 
-test('returns false when IDAT precedes acTL', (t) => {
+test('returns false when acTL is not a chunk type', (t) => {
   t.false(
     isApng(
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // IDAT
-        0x49, 0x44, 0x41, 0x54,
-        // acTL
+        // Chunk length: 4
+        0x00, 0x00, 0x00, 0x04,
+        // Chunk type: any
+        0x00, 0x00, 0x00, 0x01,
+        // Chunk data: acTL
         0x61, 0x63, 0x54, 0x4c,
       ]),
     ),
   )
 })
 
-test('returns false when missing IDAT', (t) => {
+test('returns false when IDAT precedes acTL', (t) => {
   t.false(
     isApng(
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // acTL
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: IDAT
+        0x49, 0x44, 0x41, 0x54,
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: acTL
         0x61, 0x63, 0x54, 0x4c,
       ]),
     ),
@@ -72,10 +92,10 @@ test('chunks should be found when preceded by a partial of themselves', (t) => {
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // a acTL
-        0x61, 0x61, 0x63, 0x54, 0x4c,
-        // I IDAT
-        0x49, 0x49, 0x44, 0x41, 0x54,
+        // Chunk length: a
+        0x00, 0x00, 0x00, 0x61,
+        // Chunk type: acTL
+        0x61, 0x63, 0x54, 0x4c,
       ]),
     ),
   )
diff --git a/src/index.ts b/src/index.ts
index 1cf86b3..6c58e4e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,34 @@
+function convertToInt(bytes: Uint8Array) {
+  return bytes.reduce((value, byte) => (value << 8) + byte)
+}
+
+function isEqual(first, second) {
+  return (
+    first[0] === second[0] &&
+    first[1] === second[1] &&
+    first[2] === second[2] &&
+    first[3] === second[3]
+  )
+}
+
 const encoder = new TextEncoder()
-const sequences = {
-  animationControlChunk: encoder.encode('acTL'),
-  imageDataChunk: encoder.encode('IDAT'),
+const chunkTypes = {
+  animationControl: encoder.encode('acTL'),
+  imageData: encoder.encode('IDAT'),
+}
+
+/**
+ * @see http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html
+ */
+const headerSizes = {
+  /** Number of bytes reserved for PNG signature */
+  SIGNATURE: 8,
+  /** Number of bytes reserved for chunk type */
+  LENGTH: 4,
+  /** Number of bytes reserved for chunk type */
+  TYPE: 4,
+  /** Number of bytes reserved for chunk CRC */
+  CRC: 4,
 }
 
 export default function isApng(buffer: Buffer | Uint8Array): boolean {
@@ -33,32 +60,28 @@ export default function isApng(buffer: Buffer | Uint8Array): boolean {
   // APNGs have an animation control chunk (acTL) preceding any IDAT(s).
   // See: https://en.wikipedia.org/wiki/APNG#File_format
 
-  buffer = buffer.subarray(8)
+  buffer = buffer.subarray(headerSizes.SIGNATURE)
 
-  let firstIndex = 0
-  let secondIndex = 0
-  for (let i = 0; i < buffer.length; i++) {
-    if (buffer[i] !== sequences.animationControlChunk[firstIndex]) {
-      firstIndex = 0
-    }
+  const minBufferSize = headerSizes.LENGTH + headerSizes.TYPE
+  while (buffer.length >= minBufferSize) {
+    const chunkLength = convertToInt(buffer.subarray(0, headerSizes.LENGTH))
+    const chunkType = buffer.subarray(
+      headerSizes.LENGTH,
+      headerSizes.LENGTH + headerSizes.TYPE,
+    )
 
-    if (buffer[i] === sequences.animationControlChunk[firstIndex]) {
-      firstIndex++
-      if (firstIndex === sequences.animationControlChunk.length) {
-        return true
-      }
+    if (isEqual(chunkType, chunkTypes.animationControl)) {
+      return true
     }
 
-    if (buffer[i] !== sequences.imageDataChunk[secondIndex]) {
-      secondIndex = 0
+    if (isEqual(chunkType, chunkTypes.imageData)) {
+      return false
     }
 
-    if (buffer[i] === sequences.imageDataChunk[secondIndex]) {
-      secondIndex++
-      if (secondIndex === sequences.imageDataChunk.length) {
-        return false
-      }
-    }
+    const nextChunkPosition =
+      headerSizes.LENGTH + headerSizes.TYPE + chunkLength + headerSizes.CRC
+
+    buffer = buffer.subarray(nextChunkPosition)
   }
 
   return false