diff --git a/chacha20/src/backends/neon.rs b/chacha20/src/backends/neon.rs
index 23c9207..79c3121 100644
--- a/chacha20/src/backends/neon.rs
+++ b/chacha20/src/backends/neon.rs
@@ -88,15 +88,6 @@ impl<R: Rounds> ParBlocksSizeUser for Backend<R> {
     type ParBlocksSize = U4;
 }
 
-macro_rules! add64 {
-    ($a:expr, $b:expr) => {
-        vreinterpretq_u32_u64(vaddq_u64(
-            vreinterpretq_u64_u32($a),
-            vreinterpretq_u64_u32($b),
-        ))
-    };
-}
-
 /// Evaluates to `a = a + b`, where the operands are u32x4s
 macro_rules! add_assign_vec {
     ($a:expr, $b:expr) => {
@@ -113,7 +104,7 @@ impl<R: Rounds> StreamCipherBackend for Backend<R> {
         self.gen_par_ks_blocks(&mut par);
         *block = par[0];
         unsafe {
-            self.state[3] = add64!(state3, vld1q_u32([1, 0, 0, 0].as_ptr()));
+            self.state[3] = vaddq_u32(state3, vld1q_u32([1, 0, 0, 0].as_ptr()));
         }
     }
 
@@ -126,19 +117,19 @@ impl<R: Rounds> StreamCipherBackend for Backend<R> {
                     self.state[0],
                     self.state[1],
                     self.state[2],
-                    add64!(self.state[3], self.ctrs[0]),
+                    vaddq_u32(self.state[3], self.ctrs[0]),
                 ],
                 [
                     self.state[0],
                     self.state[1],
                     self.state[2],
-                    add64!(self.state[3], self.ctrs[1]),
+                    vaddq_u32(self.state[3], self.ctrs[1]),
                 ],
                 [
                     self.state[0],
                     self.state[1],
                     self.state[2],
-                    add64!(self.state[3], self.ctrs[2]),
+                    vaddq_u32(self.state[3], self.ctrs[2]),
                 ],
             ];
 
@@ -152,7 +143,7 @@ impl<R: Rounds> StreamCipherBackend for Backend<R> {
                     add_assign_vec!(blocks[block][state_row], self.state[state_row]);
                 }
                 if block > 0 {
-                    blocks[block][3] = add64!(blocks[block][3], self.ctrs[block - 1]);
+                    blocks[block][3] = vaddq_u32(blocks[block][3], self.ctrs[block - 1]);
                 }
                 // write blocks to dest
                 for state_row in 0..4 {
@@ -162,7 +153,7 @@ impl<R: Rounds> StreamCipherBackend for Backend<R> {
                     );
                 }
             }
-            self.state[3] = add64!(self.state[3], self.ctrs[3]);
+            self.state[3] = vaddq_u32(self.state[3], self.ctrs[3]);
         }
     }
 }
@@ -205,19 +196,19 @@ impl<R: Rounds> Backend<R> {
                 self.state[0],
                 self.state[1],
                 self.state[2],
-                add64!(self.state[3], self.ctrs[0]),
+                vaddq_u32(self.state[3], self.ctrs[0]),
             ],
             [
                 self.state[0],
                 self.state[1],
                 self.state[2],
-                add64!(self.state[3], self.ctrs[1]),
+                vaddq_u32(self.state[3], self.ctrs[1]),
             ],
             [
                 self.state[0],
                 self.state[1],
                 self.state[2],
-                add64!(self.state[3], self.ctrs[2]),
+                vaddq_u32(self.state[3], self.ctrs[2]),
             ],
         ];
 
@@ -232,7 +223,7 @@ impl<R: Rounds> Backend<R> {
                 add_assign_vec!(blocks[block][state_row], self.state[state_row]);
             }
             if block > 0 {
-                blocks[block][3] = add64!(blocks[block][3], self.ctrs[block - 1]);
+                blocks[block][3] = vaddq_u32(blocks[block][3], self.ctrs[block - 1]);
             }
             // write blocks to buffer
             for state_row in 0..4 {
@@ -243,7 +234,7 @@ impl<R: Rounds> Backend<R> {
             }
             dest_ptr = dest_ptr.add(64);
         }
-        self.state[3] = add64!(self.state[3], self.ctrs[3]);
+        self.state[3] = vaddq_u32(self.state[3], self.ctrs[3]);
     }
 }
 
diff --git a/chacha20/src/rng.rs b/chacha20/src/rng.rs
index b9a4b9e..654cfb9 100644
--- a/chacha20/src/rng.rs
+++ b/chacha20/src/rng.rs
@@ -1114,5 +1114,30 @@ pub(crate) mod tests {
         rng.set_stream([3, 3333, 333333]);
         let expected = 2059058063;
         assert_eq!(rng.next_u32(), expected);
+        rng.set_stream(1234567);
+        let expected = 1254506509;
+        assert_eq!(rng.next_u32(), expected);
+        rng.set_stream([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]);
+        let expected = 1391671567;
+        assert_eq!(rng.next_u32(), expected);
+    }
+
+    /// If this test fails, the backend may be
+    /// performing 64-bit addition.
+    #[test]
+    fn counter_wrapping() {
+        let mut rng = ChaChaRng::from_seed([0u8; 32]);
+
+        // get first four blocks and word pos
+        let mut first_blocks = [0u8; 64 * 4];
+        rng.fill_bytes(&mut first_blocks);
+        let word_pos = rng.get_word_pos();
+
+        // get first four blocks after wrapping
+        rng.set_block_pos(u32::MAX);
+        let mut result = [0u8; 64 * 5];
+        rng.fill_bytes(&mut result);
+        assert_eq!(word_pos, rng.get_word_pos());
+        assert_eq!(&first_blocks[0..64 * 4], &result[64..]);
     }
 }