diff --git a/build_extra/flatbuffers/rust/BUILD.gn b/build_extra/flatbuffers/rust/BUILD.gn
index 92e3e6e71e..dd4a5c64c4 100644
--- a/build_extra/flatbuffers/rust/BUILD.gn
+++ b/build_extra/flatbuffers/rust/BUILD.gn
@@ -2,4 +2,5 @@ import("//build_extra/rust/rust.gni")
 
 rust_crate("flatbuffers") {
   source_root = "//third_party/flatbuffers/rust/flatbuffers/src/lib.rs"
+  args = [ "-Aunused_variables" ]  # TODO Remove this.
 }
diff --git a/build_extra/rust/BUILD.gn b/build_extra/rust/BUILD.gn
index 6cc239fc8e..6873195b20 100644
--- a/build_extra/rust/BUILD.gn
+++ b/build_extra/rust/BUILD.gn
@@ -69,6 +69,7 @@ rust_crate("cfg_if") {
 
 rust_crate("sha1") {
   source_root = "$registry_github/sha1-0.6.0/src/lib.rs"
+  args = [ "-Aunused_parens" ]  # https://github.com/mitsuhiko/rust-sha1/issues/36
 }
 
 rust_crate("tempfile") {
@@ -259,6 +260,11 @@ rust_crate("iovec") {
 
 rust_crate("lazycell") {
   source_root = "$registry_github/lazycell-0.6.0/src/lib.rs"
+  args = [
+    # TODO Remove these:
+    "-Aunused_unsafe",
+    "-Aunused_mut",
+  ]
 }
 
 rust_crate("net2") {
@@ -367,6 +373,11 @@ rust_crate("hyper") {
     ":tokio_timer",
     ":want",
   ]
+  args = [
+    # TODO Remove these.
+    "-Adeprecated",
+    "-Aunused_imports",
+  ]
 }
 
 rust_crate("tokio_core") {
diff --git a/libdeno/file_util_test.cc b/libdeno/file_util_test.cc
index a7b6727e17..ac854c52e1 100644
--- a/libdeno/file_util_test.cc
+++ b/libdeno/file_util_test.cc
@@ -38,7 +38,7 @@ TEST(FileUtilTest, ExePath) {
   EXPECT_TRUE(exe_path.find("/") == 0 || exe_path.find(":\\") == 1);
   // FIlename is the name of the test binary.
   std::string exe_filename = deno::Basename(exe_path);
-  EXPECT_EQ(exe_filename.find("test_cc"), 0);
+  EXPECT_EQ(exe_filename.find("test_cc"), 0u);
   // Path exists (also tests ReadFileToString).
   std::string contents;
   EXPECT_TRUE(deno::ReadFileToString(exe_path.c_str(), &contents));
diff --git a/src/handlers.rs b/src/handlers.rs
index 866ca8b3aa..7ee6018ccb 100644
--- a/src/handlers.rs
+++ b/src/handlers.rs
@@ -469,10 +469,10 @@ fn handle_read_file_sync(
 
 fn handle_write_file_sync(
   d: *const DenoC,
-  builder: &mut FlatBufferBuilder,
+  _builder: &mut FlatBufferBuilder,
   filename: &str,
   data: &[u8],
-  perm: u32,
+  _perm: u32,
 ) -> HandlerResult {
   debug!("handle_write_file_sync {}", filename);
   let deno = from_c(d);