diff --git a/crates/backend/src/codegen.rs b/crates/backend/src/codegen.rs
index d71ff6bdc..99c7aec42 100644
--- a/crates/backend/src/codegen.rs
+++ b/crates/backend/src/codegen.rs
@@ -129,7 +129,7 @@ impl ToTokens for ast::Struct {
             impl ::wasm_bindgen::convert::FromWasmAbi for #name {
                 type Abi = u32;
 
-                unsafe fn from_abi(js: u32, extra: &mut ::wasm_bindgen::convert::Stack)
+                unsafe fn from_abi(js: u32, _extra: &mut ::wasm_bindgen::convert::Stack)
                     -> Self
                 {
                     let ptr = js as *mut ::wasm_bindgen::__rt::WasmRefCell<#name>;
diff --git a/tests/all/classes.rs b/tests/all/classes.rs
index b388a5dfa..c96593f65 100644
--- a/tests/all/classes.rs
+++ b/tests/all/classes.rs
@@ -291,13 +291,13 @@ fn issue_27() {
 
             #[wasm_bindgen]
             impl Context {
-                pub fn parse(&self, expr: &str) -> Expr {
+                pub fn parse(&self, _expr: &str) -> Expr {
                     panic!()
                 }
-                pub fn eval(&self, expr: &Expr) -> f64 {
+                pub fn eval(&self, _expr: &Expr) -> f64 {
                     panic!()
                 }
-                pub fn set(&mut self, var: &str, val: f64) {
+                pub fn set(&mut self, _var: &str, _val: f64) {
                     panic!()
                 }
             }
diff --git a/tests/all/closures.rs b/tests/all/closures.rs
index 0cac95c94..d965091c1 100644
--- a/tests/all/closures.rs
+++ b/tests/all/closures.rs
@@ -294,7 +294,6 @@ fn long_fnmut_recursive() {
 
             extern crate wasm_bindgen;
 
-            use std::cell::Cell;
             use wasm_bindgen::prelude::*;
 
             #[wasm_bindgen(module = "./test")]
@@ -336,7 +335,6 @@ fn fnmut() {
 
             extern crate wasm_bindgen;
 
-            use std::cell::Cell;
             use wasm_bindgen::prelude::*;
 
             #[wasm_bindgen(module = "./test")]
@@ -385,7 +383,6 @@ fn fnmut_bad() {
 
             extern crate wasm_bindgen;
 
-            use std::cell::Cell;
             use wasm_bindgen::prelude::*;
 
             #[wasm_bindgen(module = "./test")]
@@ -441,7 +438,6 @@ fn string_arguments() {
 
             extern crate wasm_bindgen;
 
-            use std::cell::Cell;
             use wasm_bindgen::prelude::*;
 
             #[wasm_bindgen(module = "./test")]
diff --git a/tests/all/imports.rs b/tests/all/imports.rs
index b464e0898..3cd4f7fca 100644
--- a/tests/all/imports.rs
+++ b/tests/all/imports.rs
@@ -87,6 +87,7 @@ fn unused() {
     project()
         .file("src/lib.rs", r#"
             #![feature(proc_macro, wasm_custom_section, wasm_import_module)]
+            #![allow(dead_code)]
 
             extern crate wasm_bindgen;
 
diff --git a/tests/all/main.rs b/tests/all/main.rs
index 27fcdaa97..8c7aac10a 100644
--- a/tests/all/main.rs
+++ b/tests/all/main.rs
@@ -169,7 +169,9 @@ impl Project {
             .arg("--target")
             .arg("wasm32-unknown-unknown")
             .current_dir(&root)
-            .env("CARGO_TARGET_DIR", &target_dir);
+            .env("CARGO_TARGET_DIR", &target_dir)
+            // Catch any warnings in generated code because we don't want any
+            .env("RUSTFLAGS", "-Dwarnings");
         run(&mut cmd, "cargo");
 
         let idx = IDX.with(|x| *x);