diff --git a/src/device/inspect.rs b/src/device/inspect.rs
index aae1cf5..3cecde6 100644
--- a/src/device/inspect.rs
+++ b/src/device/inspect.rs
@@ -418,7 +418,7 @@ fn get_size_via_ioctl(path: &Path) -> Result<u64, WipeError> {
     let mut size: u64 = 0;
     // BLKGETSIZE64 = _IOR(0x12,114,size_t) => 0x80081272 on x86_64
     const BLKGETSIZE64: libc::c_ulong = 0x80081272;
-    let ret = unsafe { libc::ioctl(fd, BLKGETSIZE64 as libc::c_ulong, &mut size as *mut u64) };
+    let ret = unsafe { libc::ioctl(fd, BLKGETSIZE64 as _, &mut size as *mut u64 as *mut libc::c_void) };
     if ret == 0 {
         Ok(size)
     } else {