diff --git a/src/qdldl/qdldl.rs b/src/qdldl/qdldl.rs
index d3fba18..7171efb 100644
--- a/src/qdldl/qdldl.rs
+++ b/src/qdldl/qdldl.rs
@@ -738,14 +738,14 @@ fn _invperm(p: &[usize]) -> Result<Vec<usize>, QDLDLError> {
 // in both cases for safety
 
 pub(crate) fn permute<T: Copy>(x: &mut [T], b: &[T], p: &[usize]) {
-    debug_assert!(*p.iter().max().unwrap_or(&0) < x.len());
+    debug_assert!(p.is_empty() || *p.iter().max().unwrap() < x.len());
     unsafe {
         zip(p, x).for_each(|(p, x)| *x = *b.get_unchecked(*p));
     }
 }
 
 pub(crate) fn ipermute<T: Copy>(x: &mut [T], b: &[T], p: &[usize]) {
-    debug_assert!(*p.iter().max().unwrap_or(&0) < x.len());
+    debug_assert!(p.is_empty() || *p.iter().max().unwrap() < x.len());
     unsafe {
         zip(p, b).for_each(|(p, b)| *x.get_unchecked_mut(*p) = *b);
     }
diff --git a/src/qdldl/test.rs b/src/qdldl/test.rs
index c7d2ebc..8c21a78 100644
--- a/src/qdldl/test.rs
+++ b/src/qdldl/test.rs
@@ -49,7 +49,7 @@ fn test_invperm_bad_perm2() {
 
 #[test]
 fn test_permute() {
-    let perm = vec![3, 0, 2, 1]; //index too big
+    let perm = vec![3, 0, 2, 1];
     let b = vec![1., 2., 3., 4.];
     let mut x = vec![0.; 4];
     let mut y = vec![0.; 4];