diff --git a/library/compiler-builtins/libm/crates/util/src/main.rs b/library/compiler-builtins/libm/crates/util/src/main.rs
index 23aed06c00d7..889823d2e4ab 100644
--- a/library/compiler-builtins/libm/crates/util/src/main.rs
+++ b/library/compiler-builtins/libm/crates/util/src/main.rs
@@ -146,8 +146,8 @@ macro_rules! impl_parse_tuple {
 
         impl ParseTuple for ($ty, $ty, $ty) {
             fn parse(input: &[&str]) -> Self {
-                assert_eq!(input.len(), 2, "expected three arguments, got {input:?}");
-                (parse(input, 0), parse(input, 1), parse(input, 3))
+                assert_eq!(input.len(), 3, "expected three arguments, got {input:?}");
+                (parse(input, 0), parse(input, 1), parse(input, 2))
             }
         }
     };
@@ -187,8 +187,8 @@ macro_rules! impl_parse_tuple_via_rug {
 
         impl ParseTuple for ($ty, $ty, $ty) {
             fn parse(input: &[&str]) -> Self {
-                assert_eq!(input.len(), 2, "expected three arguments, got {input:?}");
-                (parse_rug(input, 0), parse_rug(input, 1), parse_rug(input, 3))
+                assert_eq!(input.len(), 3, "expected three arguments, got {input:?}");
+                (parse_rug(input, 0), parse_rug(input, 1), parse_rug(input, 2))
             }
         }
     };