diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 25c8e55..678caf5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,6 +22,7 @@ jobs:
         arch:
           - i686
           - x86_64
+          - aarch64
         features:
           - default
           - runtime-dispatch-simd
diff --git a/src/simd/aarch64.rs b/src/simd/aarch64.rs
index 56e8b71..6544355 100644
--- a/src/simd/aarch64.rs
+++ b/src/simd/aarch64.rs
@@ -1,5 +1,6 @@
 use core::arch::aarch64::{
-    uint8x16_t, vaddlvq_u8, vandq_u8, vceqq_u8, vcgtq_u8, vdupq_n_u8, vld1q_u8, vmvnq_u8, vsubq_u8,
+    uint8x16_t, uint8x16x4_t, vaddlvq_u8, vandq_u8, vceqq_u8, vdupq_n_u8, vld1q_u8, vld1q_u8_x4,
+    vmvnq_u8, vsubq_u8,
 };
 
 const MASK: [u8; 32] = [
@@ -9,12 +10,29 @@ const MASK: [u8; 32] = [
 
 #[target_feature(enable = "neon")]
 unsafe fn u8x16_from_offset(slice: &[u8], offset: usize) -> uint8x16_t {
+    debug_assert!(
+        offset + 16 <= slice.len(),
+        "{} + 16 ≥ {}",
+        offset,
+        slice.len()
+    );
     vld1q_u8(slice.as_ptr().add(offset) as *const _) // TODO: does this need to be aligned?
 }
 
 #[target_feature(enable = "neon")]
-unsafe fn sum(u8s: &uint8x16_t) -> usize {
-    vaddlvq_u8(*u8s) as usize
+unsafe fn u8x16_x4_from_offset(slice: &[u8], offset: usize) -> uint8x16x4_t {
+    debug_assert!(
+        offset + 64 <= slice.len(),
+        "{} + 64 ≥ {}",
+        offset,
+        slice.len()
+    );
+    vld1q_u8_x4(slice.as_ptr().add(offset) as *const _)
+}
+
+#[target_feature(enable = "neon")]
+unsafe fn sum(u8s: uint8x16_t) -> usize {
+    vaddlvq_u8(u8s) as usize
 }
 
 #[target_feature(enable = "neon")]
@@ -26,38 +44,40 @@ pub unsafe fn chunk_count(haystack: &[u8], needle: u8) -> usize {
 
     let needles = vdupq_n_u8(needle);
 
-    // 4080
-    while haystack.len() >= offset + 16 * 255 {
-        let mut counts = vdupq_n_u8(0);
+    // 16320
+    while haystack.len() >= offset + 64 * 255 {
+        let (mut count1, mut count2, mut count3, mut count4) =
+            (vdupq_n_u8(0), vdupq_n_u8(0), vdupq_n_u8(0), vdupq_n_u8(0));
         for _ in 0..255 {
-            counts = vsubq_u8(
-                counts,
-                vceqq_u8(u8x16_from_offset(haystack, offset), needles),
-            );
-            offset += 16;
+            let uint8x16x4_t(h1, h2, h3, h4) = u8x16_x4_from_offset(haystack, offset);
+            count1 = vsubq_u8(count1, vceqq_u8(h1, needles));
+            count2 = vsubq_u8(count2, vceqq_u8(h2, needles));
+            count3 = vsubq_u8(count3, vceqq_u8(h3, needles));
+            count4 = vsubq_u8(count4, vceqq_u8(h4, needles));
+            offset += 64;
         }
-        count += sum(&counts);
+        count += sum(count1) + sum(count2) + sum(count3) + sum(count4);
     }
 
-    // 2048
-    if haystack.len() >= offset + 16 * 128 {
-        let mut counts = vdupq_n_u8(0);
-        for _ in 0..128 {
-            counts = vsubq_u8(
-                counts,
-                vceqq_u8(u8x16_from_offset(haystack, offset), needles),
-            );
-            offset += 16;
-        }
-        count += sum(&counts);
+    // 64
+    let (mut count1, mut count2, mut count3, mut count4) =
+        (vdupq_n_u8(0), vdupq_n_u8(0), vdupq_n_u8(0), vdupq_n_u8(0));
+    for _ in 0..(haystack.len() - offset) / 64 {
+        let uint8x16x4_t(h1, h2, h3, h4) = u8x16_x4_from_offset(haystack, offset);
+        count1 = vsubq_u8(count1, vceqq_u8(h1, needles));
+        count2 = vsubq_u8(count2, vceqq_u8(h2, needles));
+        count3 = vsubq_u8(count3, vceqq_u8(h3, needles));
+        count4 = vsubq_u8(count4, vceqq_u8(h4, needles));
+        offset += 64;
     }
+    count += sum(count1) + sum(count2) + sum(count3) + sum(count4);
 
-    // 16
     let mut counts = vdupq_n_u8(0);
+    // 16
     for i in 0..(haystack.len() - offset) / 16 {
         counts = vsubq_u8(
             counts,
-            vcgtq_u8(u8x16_from_offset(haystack, offset + i * 32), needles),
+            vceqq_u8(u8x16_from_offset(haystack, offset + i * 16), needles),
         );
     }
     if haystack.len() % 16 != 0 {
@@ -69,9 +89,7 @@ pub unsafe fn chunk_count(haystack: &[u8], needle: u8) -> usize {
             ),
         );
     }
-    count += sum(&counts);
-
-    count
+    count + sum(counts)
 }
 
 #[target_feature(enable = "neon")]
@@ -100,7 +118,7 @@ pub unsafe fn chunk_num_chars(utf8_chars: &[u8]) -> usize {
             );
             offset += 16;
         }
-        count += sum(&counts);
+        count += sum(counts);
     }
 
     // 2048
@@ -113,7 +131,7 @@ pub unsafe fn chunk_num_chars(utf8_chars: &[u8]) -> usize {
             );
             offset += 16;
         }
-        count += sum(&counts);
+        count += sum(counts);
     }
 
     // 16
@@ -121,7 +139,7 @@ pub unsafe fn chunk_num_chars(utf8_chars: &[u8]) -> usize {
     for i in 0..(utf8_chars.len() - offset) / 16 {
         counts = vsubq_u8(
             counts,
-            is_leading_utf8_byte(u8x16_from_offset(utf8_chars, offset + i * 32)),
+            is_leading_utf8_byte(u8x16_from_offset(utf8_chars, offset + i * 16)),
         );
     }
     if utf8_chars.len() % 16 != 0 {
@@ -133,7 +151,7 @@ pub unsafe fn chunk_num_chars(utf8_chars: &[u8]) -> usize {
             ),
         );
     }
-    count += sum(&counts);
+    count += sum(counts);
 
     count
 }