diff --git a/src/acpi/aml/type2opcode.rs b/src/acpi/aml/type2opcode.rs
index bd7fb47..5c37652 100644
--- a/src/acpi/aml/type2opcode.rs
+++ b/src/acpi/aml/type2opcode.rs
@@ -1589,7 +1589,7 @@ fn parse_def_mid(data: &[u8],
                 let mut res = s.clone().split_off(idx);
 
                 if len < res.len() {
-                    res.split_off(len);
+                    res.split_off(len).clear();
                 }
 
                 AmlValue::String(res)
diff --git a/src/lib.rs b/src/lib.rs
index f4e8d91..d56cac0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,6 +39,8 @@
 // This is usually a serious issue - a missing import of a define where it is interpreted
 // as a catch-all variable in a match, for example
 #![deny(unreachable_patterns)]
+// Ensure that all must_use results are used
+#![deny(unused_must_use)]
 
 #![feature(allocator_api)]
 #![feature(asm)] // TODO: Relax requirements of most asm invocations