diff --git a/CHANGELOG.md b/CHANGELOG.md
index d21f26cbb7..2a0a5397d8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,9 @@ of panicking drop implementations.
 - Added `CString::{into_bytes, into_bytes_with_nul, into_string}`
 - Added `pop_front_if` and `pop_back_if` to `Deque`
 - Made `Vec::from_array` const.
+- Fixed long division being instroduced by the const-erasure in spsc
+- spsc: Fix integer overflow in iterators when N > usize::MAX/2 and the queue loops.
+- spsc: Fix integer overflow leading to a panic in `len` when N == usize::MAX and debug assertions are enabled.
 
 ## [v0.9.2] 2025-11-12
 
diff --git a/src/spsc.rs b/src/spsc.rs
index 6eb6fde4d7..25b31a6f3a 100644
--- a/src/spsc.rs
+++ b/src/spsc.rs
@@ -129,12 +129,6 @@ pub struct QueueInner<T, S: Storage> {
 /// A statically allocated single-producer, single-consumer queue with a capacity of `N - 1`
 /// elements.
 ///
-/// <div class="warning">
-///
-/// To get better performance, use a value for `N` that is a power of 2.
-///
-/// </div>
-///
 /// You will likely want to use [`split`](QueueInner::split) to create a producer-consumer pair.
 pub type Queue<T, const N: usize> = QueueInner<T, OwnedStorage<N>>;
 
@@ -182,7 +176,15 @@ impl<T, S: Storage> QueueInner<T, S> {
 
     #[inline]
     fn increment(&self, val: usize) -> usize {
-        (val + 1) % self.n()
+        // We know that self.n() <= usize::MAX
+        // So this can only overflow if N == usize::MAX
+        // and in this case the overflow will be equivalent to the modulo N operation
+        let val = val.wrapping_add(1);
+        if val >= self.n() {
+            val - self.n()
+        } else {
+            val
+        }
     }
 
     #[inline]
@@ -202,10 +204,13 @@ impl<T, S: Storage> QueueInner<T, S> {
         let current_head = self.head.load(Ordering::Relaxed);
         let current_tail = self.tail.load(Ordering::Relaxed);
 
-        current_tail
-            .wrapping_sub(current_head)
-            .wrapping_add(self.n())
-            % self.n()
+        if current_tail >= current_head {
+            current_tail - current_head
+        } else {
+            current_tail
+                .wrapping_sub(current_head)
+                .wrapping_add(self.n())
+        }
     }
 
     /// Returns whether the queue is empty.
@@ -626,7 +631,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
         if self.index < self.len {
             let head = self.rb.head.load(Ordering::Relaxed);
 
-            let i = (head + self.index) % self.rb.n();
+            let i = match head.checked_add(self.index) {
+                Some(i) if i >= self.rb.n() => i - self.rb.n(),
+                Some(i) => i,
+                None => head.wrapping_add(self.index).wrapping_sub(self.rb.n()),
+            };
             self.index += 1;
 
             Some(unsafe { &*(self.rb.buffer.borrow().get_unchecked(i).get() as *const T) })
@@ -643,7 +652,11 @@ impl<'a, T> Iterator for IterMut<'a, T> {
         if self.index < self.len {
             let head = self.rb.head.load(Ordering::Relaxed);
 
-            let i = (head + self.index) % self.rb.n();
+            let i = match head.checked_add(self.index) {
+                Some(i) if i >= self.rb.n() => i - self.rb.n(),
+                Some(i) => i,
+                None => head.wrapping_add(self.index).wrapping_sub(self.rb.n()),
+            };
             self.index += 1;
 
             Some(unsafe { &mut *self.rb.buffer.borrow().get_unchecked(i).get().cast::<T>() })
@@ -659,7 +672,11 @@ impl<T> DoubleEndedIterator for Iter<'_, T> {
             let head = self.rb.head.load(Ordering::Relaxed);
 
             // self.len > 0, since it's larger than self.index > 0
-            let i = (head + self.len - 1) % self.rb.n();
+            let i = match head.checked_add(self.len - 1) {
+                Some(i) if i >= self.rb.n() => i - self.rb.n(),
+                Some(i) => i,
+                None => head.wrapping_add(self.len - 1).wrapping_sub(self.rb.n()),
+            };
             self.len -= 1;
             Some(unsafe { &*(self.rb.buffer.borrow().get_unchecked(i).get() as *const T) })
         } else {
@@ -674,7 +691,11 @@ impl<T> DoubleEndedIterator for IterMut<'_, T> {
             let head = self.rb.head.load(Ordering::Relaxed);
 
             // self.len > 0, since it's larger than self.index > 0
-            let i = (head + self.len - 1) % self.rb.n();
+            let i = match head.checked_add(self.len - 1) {
+                Some(i) if i >= self.rb.n() => i - self.rb.n(),
+                Some(i) => i,
+                None => head.wrapping_add(self.len - 1).wrapping_sub(self.rb.n()),
+            };
             self.len -= 1;
             Some(unsafe { &mut *self.rb.buffer.borrow().get_unchecked(i).get().cast::<T>() })
         } else {
@@ -882,9 +903,19 @@ impl<T> Producer<'_, T> {
 
 #[cfg(test)]
 mod tests {
-    use std::hash::{Hash, Hasher};
+    use std::{
+        cell::UnsafeCell,
+        hash::{Hash, Hasher},
+        mem::MaybeUninit,
+    };
 
     use super::{Consumer, Producer, Queue};
+    #[cfg(not(feature = "portable-atomic"))]
+    use core::sync::atomic;
+    #[cfg(feature = "portable-atomic")]
+    use portable_atomic as atomic;
+
+    use atomic::AtomicUsize;
 
     use static_assertions::assert_not_impl_any;
 
@@ -1076,6 +1107,28 @@ mod tests {
         assert_eq!(items.next(), None);
     }
 
+    /// Exercise the modulo `self.n()` operation in `next()`
+    #[test]
+    fn iter_modulo() {
+        let mut rb: Queue<i32, 4> = Queue::new();
+
+        for _ in 0..2 {
+            rb.enqueue(0).unwrap();
+            rb.dequeue().unwrap();
+        }
+        rb.enqueue(1).unwrap();
+        rb.enqueue(2).unwrap();
+        rb.enqueue(3).unwrap();
+
+        let mut items = rb.iter();
+
+        // assert_eq!(items.next(), Some(&0));
+        assert_eq!(items.next(), Some(&1));
+        assert_eq!(items.next(), Some(&2));
+        assert_eq!(items.next(), Some(&3));
+        assert_eq!(items.next(), None);
+    }
+
     #[test]
     fn iter_double_ended() {
         let mut rb: Queue<i32, 4> = Queue::new();
@@ -1093,6 +1146,28 @@ mod tests {
         assert_eq!(items.next_back(), None);
     }
 
+    /// Test that the modulo in `next_back` works as expected
+    #[test]
+    fn iter_double_ended_modulo() {
+        let mut rb: Queue<i32, 4> = Queue::new();
+
+        for _ in 0..2 {
+            rb.enqueue(0).unwrap();
+            rb.dequeue().unwrap();
+        }
+        rb.enqueue(0).unwrap();
+        rb.enqueue(1).unwrap();
+        rb.enqueue(2).unwrap();
+
+        let mut items = rb.iter();
+
+        assert_eq!(items.next(), Some(&0));
+        assert_eq!(items.next_back(), Some(&2));
+        assert_eq!(items.next(), Some(&1));
+        assert_eq!(items.next(), None);
+        assert_eq!(items.next_back(), None);
+    }
+
     #[test]
     fn iter_mut() {
         let mut rb: Queue<i32, 4> = Queue::new();
@@ -1126,6 +1201,28 @@ mod tests {
         assert_eq!(items.next_back(), None);
     }
 
+    /// Test that the modulo in `next_back` works as expected
+    #[test]
+    fn iter_mut_double_ended_modulo() {
+        let mut rb: Queue<i32, 4> = Queue::new();
+
+        for _ in 0..2 {
+            rb.enqueue(0).unwrap();
+            rb.dequeue().unwrap();
+        }
+        rb.enqueue(0).unwrap();
+        rb.enqueue(1).unwrap();
+        rb.enqueue(2).unwrap();
+
+        let mut items = rb.iter_mut();
+
+        assert_eq!(items.next(), Some(&mut 0));
+        assert_eq!(items.next_back(), Some(&mut 2));
+        assert_eq!(items.next(), Some(&mut 1));
+        assert_eq!(items.next(), None);
+        assert_eq!(items.next_back(), None);
+    }
+
     #[test]
     fn wrap_around() {
         let mut rb: Queue<i32, 4> = Queue::new();
@@ -1238,4 +1335,74 @@ mod tests {
         };
         assert_eq!(hash1, hash2);
     }
+
+    // Test for some integer overflow bugs. See
+    // https://github.com/rust-embedded/heapless/pull/652#discussion_r3046630717
+    // for more info
+    #[test]
+    #[cfg_attr(miri, ignore)] // too slow
+    fn test_len_overflow() {
+        let mut queue = Queue::<(), { usize::MAX }> {
+            head: AtomicUsize::new(usize::MAX),
+            tail: AtomicUsize::new(2),
+            buffer: [const { UnsafeCell::new(MaybeUninit::new(())) }; usize::MAX],
+        };
+        queue.enqueue(()).unwrap();
+        queue.enqueue(()).unwrap();
+
+        let collected: Vec<_> = queue.iter().collect();
+        assert_eq!(&collected, &[&(); 4]);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)] // too slow
+    fn test_usize_overflow_iter() {
+        let queue = Queue::<(), { usize::MAX - 1 }> {
+            head: AtomicUsize::new(usize::MAX - 3),
+            tail: AtomicUsize::new(2),
+            buffer: [const { UnsafeCell::new(MaybeUninit::new(())) }; usize::MAX - 1],
+        };
+
+        let collected: Vec<_> = queue.iter().collect();
+        assert_eq!(&collected, &[&(); 4]);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)] // too slow
+    fn test_usize_overflow_iter_mut() {
+        let mut queue = Queue::<(), { usize::MAX - 1 }> {
+            head: AtomicUsize::new(usize::MAX - 3),
+            tail: AtomicUsize::new(2),
+            buffer: [const { UnsafeCell::new(MaybeUninit::new(())) }; usize::MAX - 1],
+        };
+
+        let collected: Vec<_> = queue.iter_mut().collect();
+        assert_eq!(&collected, &[&(); 4]);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)] // too slow
+    fn test_usize_overflow_iter_rev() {
+        let queue = Queue::<(), { usize::MAX - 1 }> {
+            head: AtomicUsize::new(usize::MAX - 3),
+            tail: AtomicUsize::new(2),
+            buffer: [const { UnsafeCell::new(MaybeUninit::new(())) }; usize::MAX - 1],
+        };
+
+        let collected: Vec<_> = queue.iter().rev().collect();
+        assert_eq!(&collected, &[&(); 4]);
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)] // too slow
+    fn test_usize_overflow_iter_mut_rev() {
+        let mut queue = Queue::<(), { usize::MAX - 1 }> {
+            head: AtomicUsize::new(usize::MAX - 3),
+            tail: AtomicUsize::new(2),
+            buffer: [const { UnsafeCell::new(MaybeUninit::new(())) }; usize::MAX - 1],
+        };
+
+        let collected: Vec<_> = queue.iter_mut().rev().collect();
+        assert_eq!(&collected, &[&(); 4]);
+    }
 }