diff --git a/compiler/rustc_driver/src/lib.rs b/compiler/rustc_driver/src/lib.rs
index 179a184536e..1a7972716d3 100644
--- a/compiler/rustc_driver/src/lib.rs
+++ b/compiler/rustc_driver/src/lib.rs
@@ -1055,13 +1055,7 @@ pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
     }
 
     if cg_flags.iter().any(|x| *x == "passes=list") {
-        let backend_name = debug_flags.iter().find_map(|x| {
-            if x.starts_with("codegen-backend=") {
-                Some(&x["codegen-backends=".len()..])
-            } else {
-                None
-            }
-        });
+        let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
         get_codegen_backend(&None, backend_name).print_passes();
         return None;
     }