diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
index c370dbbd5..417145265 100644
--- a/runtime/src/lib.rs
+++ b/runtime/src/lib.rs
@@ -39,11 +39,11 @@ lazy_static! {
 #[no_mangle]
 #[allow(clippy::missing_safety_doc)]
 pub unsafe extern "C" fn cairo_native__get_version(target: *mut u8, length: usize) -> usize {
-    let target = slice::from_raw_parts_mut(target, length);
-
     let version = env!("CARGO_PKG_VERSION");
     assert!(length > version.len(), "version buffer not big enough");
 
+    let target = slice::from_raw_parts_mut(target, version.len());
+
     target.copy_from_slice(version.as_bytes());
     target[version.len()] = b'\0';