diff --git a/src/windows.rs b/src/windows.rs
index 5cc93c77..ccfc3c27 100644
--- a/src/windows.rs
+++ b/src/windows.rs
@@ -21,7 +21,7 @@ extern "system" {
     ) -> u32;
 }
 
-pub unsafe fn getrandom_inner(mut dst: *mut u8, mut len: usize) -> Result<(), Error> {
+pub unsafe fn getrandom_inner(dst: *mut u8, len: usize) -> Result<(), Error> {
     // Prevent overflow of u32
     raw_chunks(dst, len, u32::max_value() as usize, |cdst, clen| {
         // BCryptGenRandom was introduced in Windows Vista