diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index f1a160250db..0f5fcb4af40 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1490,7 +1490,7 @@ impl<'a> Builder<'a> {
                 for el in stack.iter().rev() {
                     out += &format!("\t{:?}\n", el);
                 }
-                panic!(out);
+                panic!("{}", out);
             }
             if let Some(out) = self.cache.get(&step) {
                 self.verbose(&format!("{}c {:?}", "  ".repeat(stack.len()), step));