diff --git a/tests/ui/strlen_on_c_strings.fixed b/tests/ui/strlen_on_c_strings.fixed
new file mode 100644
index 00000000000..947a59bcc02
--- /dev/null
+++ b/tests/ui/strlen_on_c_strings.fixed
@@ -0,0 +1,34 @@
+// run-rustfix
+
+#![warn(clippy::strlen_on_c_strings)]
+#![allow(dead_code)]
+#![feature(rustc_private)]
+extern crate libc;
+
+#[allow(unused)]
+use libc::strlen;
+use std::ffi::{CStr, CString};
+
+fn main() {
+    // CString
+    let cstring = CString::new("foo").expect("CString::new failed");
+    let _ = cstring.as_bytes().len();
+
+    // CStr
+    let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
+    let _ = cstr.to_bytes().len();
+
+    let _ = cstr.to_bytes().len();
+
+    let pcstr: *const &CStr = &cstr;
+    let _ = unsafe { (*pcstr).to_bytes().len() };
+
+    unsafe fn unsafe_identity<T>(x: T) -> T {
+        x
+    }
+    let _ = unsafe { unsafe_identity(cstr).to_bytes().len() };
+    let _ = unsafe { unsafe_identity(cstr) }.to_bytes().len();
+
+    let f: unsafe fn(_) -> _ = unsafe_identity;
+    let _ = unsafe { f(cstr).to_bytes().len() };
+}
diff --git a/tests/ui/strlen_on_c_strings.rs b/tests/ui/strlen_on_c_strings.rs
index a3451d992a0..1237f1ab03a 100644
--- a/tests/ui/strlen_on_c_strings.rs
+++ b/tests/ui/strlen_on_c_strings.rs
@@ -1,31 +1,34 @@
+// run-rustfix
+
 #![warn(clippy::strlen_on_c_strings)]
 #![allow(dead_code)]
 #![feature(rustc_private)]
 extern crate libc;
 
+#[allow(unused)]
 use libc::strlen;
 use std::ffi::{CStr, CString};
 
 fn main() {
     // CString
     let cstring = CString::new("foo").expect("CString::new failed");
-    let len = unsafe { libc::strlen(cstring.as_ptr()) };
+    let _ = unsafe { libc::strlen(cstring.as_ptr()) };
 
     // CStr
     let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
-    let len = unsafe { libc::strlen(cstr.as_ptr()) };
+    let _ = unsafe { libc::strlen(cstr.as_ptr()) };
 
-    let len = unsafe { strlen(cstr.as_ptr()) };
+    let _ = unsafe { strlen(cstr.as_ptr()) };
 
     let pcstr: *const &CStr = &cstr;
-    let len = unsafe { strlen((*pcstr).as_ptr()) };
+    let _ = unsafe { strlen((*pcstr).as_ptr()) };
 
     unsafe fn unsafe_identity<T>(x: T) -> T {
         x
     }
-    let len = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
-    let len = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
+    let _ = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
+    let _ = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
 
     let f: unsafe fn(_) -> _ = unsafe_identity;
-    let len = unsafe { strlen(f(cstr).as_ptr()) };
+    let _ = unsafe { strlen(f(cstr).as_ptr()) };
 }
diff --git a/tests/ui/strlen_on_c_strings.stderr b/tests/ui/strlen_on_c_strings.stderr
index 0dbecda62e3..296268a5f1d 100644
--- a/tests/ui/strlen_on_c_strings.stderr
+++ b/tests/ui/strlen_on_c_strings.stderr
@@ -1,46 +1,46 @@
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:12:15
+  --> $DIR/strlen_on_c_strings.rs:15:13
    |
-LL |     let len = unsafe { libc::strlen(cstring.as_ptr()) };
-   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstring.as_bytes().len()`
+LL |     let _ = unsafe { libc::strlen(cstring.as_ptr()) };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstring.as_bytes().len()`
    |
    = note: `-D clippy::strlen-on-c-strings` implied by `-D warnings`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:16:15
+  --> $DIR/strlen_on_c_strings.rs:19:13
    |
-LL |     let len = unsafe { libc::strlen(cstr.as_ptr()) };
-   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
+LL |     let _ = unsafe { libc::strlen(cstr.as_ptr()) };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:18:15
+  --> $DIR/strlen_on_c_strings.rs:21:13
    |
-LL |     let len = unsafe { strlen(cstr.as_ptr()) };
-   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
+LL |     let _ = unsafe { strlen(cstr.as_ptr()) };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:21:24
+  --> $DIR/strlen_on_c_strings.rs:24:22
    |
-LL |     let len = unsafe { strlen((*pcstr).as_ptr()) };
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(*pcstr).to_bytes().len()`
+LL |     let _ = unsafe { strlen((*pcstr).as_ptr()) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(*pcstr).to_bytes().len()`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:26:24
+  --> $DIR/strlen_on_c_strings.rs:29:22
    |
-LL |     let len = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe_identity(cstr).to_bytes().len()`
+LL |     let _ = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe_identity(cstr).to_bytes().len()`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:27:15
+  --> $DIR/strlen_on_c_strings.rs:30:13
    |
-LL |     let len = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
-   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe { unsafe_identity(cstr) }.to_bytes().len()`
+LL |     let _ = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe { unsafe_identity(cstr) }.to_bytes().len()`
 
 error: using `libc::strlen` on a `CString` or `CStr` value
-  --> $DIR/strlen_on_c_strings.rs:30:24
+  --> $DIR/strlen_on_c_strings.rs:33:22
    |
-LL |     let len = unsafe { strlen(f(cstr).as_ptr()) };
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `f(cstr).to_bytes().len()`
+LL |     let _ = unsafe { strlen(f(cstr).as_ptr()) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `f(cstr).to_bytes().len()`
 
 error: aborting due to 7 previous errors