diff --git a/src/utils.rs b/src/utils.rs
index 82fbb8d5925ad..5807d4c158cac 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -23,11 +23,10 @@ use rewrite::{Rewrite, RewriteContext};
 use SKIP_ANNOTATION;
 
 // Computes the length of a string's last line, minus offset.
-#[inline]
 pub fn extra_offset(text: &str, offset: Indent) -> usize {
     match text.rfind('\n') {
         // 1 for newline character
-        Some(idx) => text.len() - idx - 1 - offset.width(),
+        Some(idx) => text.len().checked_sub(idx + 1 + offset.width()).unwrap_or(0),
         None => text.len(),
     }
 }
diff --git a/tests/target/issue-1055.rs b/tests/target/issue-1055.rs
new file mode 100644
index 0000000000000..fed7d7de393fa
--- /dev/null
+++ b/tests/target/issue-1055.rs
@@ -0,0 +1,4 @@
+fn issue_1055() {
+    let foo = (|| {
+    })();
+}