diff --git a/src/util.rs b/src/util.rs
index 8d1814b07ec2681d7839923dbbc36b1458676ad6..be45a0e2bb04c8b7d12facdab77fa107e3c193e5 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -119,8 +119,8 @@ pub fn save_bmp(path: &str, pixels: &[u8], width: u32, height: u32) -> Result<()
 /// This function is optimized for performance and uses pointer-based
 /// operations to copy the data as fast as possible.
 pub fn copy_fast(src: &[u8], dst: &mut [u8], count: usize) {
-    debug_assert!(src.len() >= count);
-    debug_assert!(dst.len() >= count);
+    assert!(src.len() >= count);
+    assert!(dst.len() >= count);
 
     unsafe {
         let src_ptr = src.as_ptr();