diff --git a/protobuf/build.rs b/protobuf/build.rs
index 3494f0753..179184ac5 100644
--- a/protobuf/build.rs
+++ b/protobuf/build.rs
@@ -7,48 +7,6 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::process;
 
-// % rustc +stable --version
-// rustc 1.26.0 (a77568041 2018-05-07)
-// % rustc +beta --version
-// rustc 1.27.0-beta.1 (03fb2f447 2018-05-09)
-// % rustc +nightly --version
-// rustc 1.27.0-nightly (acd3871ba 2018-05-10)
-fn version_is_nightly(version: &str) -> bool {
-    version.contains("nightly")
-}
-
-fn cfg_rust_version() {
-    let rustc = env::var("RUSTC").expect("RUSTC unset");
-    let mut cmd = if let Some(wrapper) = env::var_os("RUSTC_WRAPPER").filter(|w| !w.is_empty()) {
-        let mut cmd = process::Command::new(wrapper);
-        cmd.arg(rustc);
-        cmd
-    } else {
-        process::Command::new(rustc)
-    };
-
-    let mut child = cmd
-        .args(&["--version"])
-        .stdin(process::Stdio::null())
-        .stdout(process::Stdio::piped())
-        .spawn()
-        .expect("spawn rustc");
-
-    let mut rustc_version = String::new();
-
-    child
-        .stdout
-        .as_mut()
-        .expect("stdout")
-        .read_to_string(&mut rustc_version)
-        .expect("read_to_string");
-    assert!(child.wait().expect("wait").success());
-
-    if version_is_nightly(&rustc_version) {
-        println!("cargo:rustc-cfg=rustc_nightly");
-    }
-}
-
 fn cfg_serde() {
     match env::var("CARGO_FEATURE_WITH_SERDE") {
         Ok(_) => {