diff --git a/lib/c-api/src/wasm_c_api/macros.rs b/lib/c-api/src/wasm_c_api/macros.rs
index 49989acd7..0feab8cd3 100644
--- a/lib/c-api/src/wasm_c_api/macros.rs
+++ b/lib/c-api/src/wasm_c_api/macros.rs
@@ -341,21 +341,21 @@ int main() {
 
 See the [`wasm_" $name "_vec_t`] type to get an example."]
             #[no_mangle]
-            pub unsafe extern "C" fn [<wasm_ $name _vec_delete>](ptr: *mut [<wasm_ $name _vec_t>]) {
-                let vec = &mut *ptr;
+            pub unsafe extern "C" fn [<wasm_ $name _vec_delete>](ptr: Option<&mut [<wasm_ $name _vec_t>]>) {
+                if let Some(vec) = ptr {
+                    if !vec.data.is_null() {
+                        let data: Vec<*mut [<wasm_ $name _t>]> = Vec::from_raw_parts(vec.data, vec.size, vec.size);
 
-                if !vec.data.is_null() {
-                    let data: Vec<*mut [<wasm_ $name _t>]> = Vec::from_raw_parts(vec.data, vec.size, vec.size);
+                        // If the vector has been initialized (we check
+                        // only the first item), we can transmute items to
+                        // `Box`es.
+                        if vec.size > 0 && !data[0].is_null() {
+                            let _data: Vec<Box<[<wasm_ $name _t>]>> = ::std::mem::transmute(data);
+                        }
 
-                    // If the vector has been initialized (we check
-                    // only the first item), we can transmute items to
-                    // `Box`es.
-                    if vec.size > 0 && !data[0].is_null() {
-                        let _data: Vec<Box<[<wasm_ $name _t>]>> = ::std::mem::transmute(data);
+                        vec.data = ::std::ptr::null_mut();
+                        vec.size = 0;
                     }
-
-                    vec.data = ::std::ptr::null_mut();
-                    vec.size = 0;
                 }
             }
         }