Generalize Type::SliceRefU8 to Type::SliceRef
diff --git a/syntax/improper.rs b/syntax/improper.rs
index 95cf4af..e0e5154 100644
--- a/syntax/improper.rs
+++ b/syntax/improper.rs
@@ -27,7 +27,7 @@
             | Type::Str(_)
             | Type::Fn(_)
             | Type::Void(_)
-            | Type::SliceRefU8(_) => Definite(true),
+            | Type::SliceRef(_) => Definite(true),
             Type::UniquePtr(_) | Type::CxxVector(_) => Definite(false),
             Type::Ref(ty) => self.determine_improper_ctype(&ty.inner),
             Type::Array(ty) => self.determine_improper_ctype(&ty.inner),