diff --git a/library/compiler-builtins/libm/crates/util/src/main.rs b/library/compiler-builtins/libm/crates/util/src/main.rs
index a519713c0b1c..710adbb17945 100644
--- a/library/compiler-builtins/libm/crates/util/src/main.rs
+++ b/library/compiler-builtins/libm/crates/util/src/main.rs
@@ -274,7 +274,7 @@ fn parse<T: FromStr + FromStrRadix>(input: &[&str], idx: usize) -> T {
 
     let msg = || format!("invalid {} input '{s}'", type_name::<T>());
 
-    if s.starts_with("0x") {
+    if s.starts_with("0x") || s.starts_with("-0x") {
         return T::from_str_radix(s, 16).unwrap_or_else(|_| panic!("{}", msg()));
     }