diff --git a/src/bootstrap/bin/sccache-plus-cl.rs b/src/bootstrap/bin/sccache-plus-cl.rs
index 5684a565a9c0e..266dffa5c92c7 100644
--- a/src/bootstrap/bin/sccache-plus-cl.rs
+++ b/src/bootstrap/bin/sccache-plus-cl.rs
@@ -24,6 +24,7 @@ fn main() {
        .target(&target)
        .host(&target)
        .opt_level(0)
+       .warnings(false)
        .debug(false);
     let compiler = cfg.get_compiler();
 
diff --git a/src/bootstrap/cc.rs b/src/bootstrap/cc.rs
index 2541950d6c75e..c77e609d70be0 100644
--- a/src/bootstrap/cc.rs
+++ b/src/bootstrap/cc.rs
@@ -46,7 +46,7 @@ pub fn find(build: &mut Build) {
     // and such as well as for being a linker for Rust code.
     for target in build.targets.iter().chain(&build.hosts).cloned().chain(iter::once(build.build)) {
         let mut cfg = gcc::Build::new();
-        cfg.cargo_metadata(false).opt_level(0).debug(false)
+        cfg.cargo_metadata(false).opt_level(0).warnings(false).debug(false)
            .target(&target).host(&build.build);
 
         let config = build.config.target_config.get(&target);
@@ -68,7 +68,7 @@ pub fn find(build: &mut Build) {
     // For all host triples we need to find a C++ compiler as well
     for host in build.hosts.iter().cloned().chain(iter::once(build.build)) {
         let mut cfg = gcc::Build::new();
-        cfg.cargo_metadata(false).opt_level(0).debug(false).cpp(true)
+        cfg.cargo_metadata(false).opt_level(0).warnings(false).debug(false).cpp(true)
            .target(&host).host(&build.build);
         let config = build.config.target_config.get(&host);
         if let Some(cxx) = config.and_then(|c| c.cxx.as_ref()) {
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index 0d1bcabc7452e..d9dc9df823a56 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -306,6 +306,7 @@ impl Step for TestHelpers {
            .target(&target)
            .host(&build.build)
            .opt_level(0)
+           .warnings(false)
            .debug(false)
            .file(build.src.join("src/rt/rust_test_helpers.c"))
            .compile("librust_test_helpers.a");
diff --git a/src/librustc_llvm/build.rs b/src/librustc_llvm/build.rs
index 9aa4ff1aefcc7..393aa7fa43bab 100644
--- a/src/librustc_llvm/build.rs
+++ b/src/librustc_llvm/build.rs
@@ -137,6 +137,7 @@ fn main() {
     cmd.arg("--cxxflags");
     let cxxflags = output(&mut cmd);
     let mut cfg = gcc::Build::new();
+    cfg.warnings(false);
     for flag in cxxflags.split_whitespace() {
         // Ignore flags like `-m64` when we're doing a cross build
         if is_crossed && flag.starts_with("-m") {