diff --git a/src/binding.rs b/src/binding.rs
index 62d727627b30f9..fc57200c39f22c 100644
--- a/src/binding.rs
+++ b/src/binding.rs
@@ -37,7 +37,11 @@ extern "C" {
         js_source: *const c_char,
     ) -> c_int;
     pub fn deno_handle_msg_from_js(d: *const DenoC, buf: deno_buf);
-    pub fn deno_reply_error(d: *const DenoC, cmd_id: uint32_t, msg: *const c_char);
+    pub fn deno_reply_error(
+        d: *const DenoC,
+        cmd_id: uint32_t,
+        msg: *const c_char,
+    );
     pub fn deno_reply_null(d: *const DenoC, cmd_id: uint32_t);
     pub fn deno_reply_code_fetch(
         d: *const DenoC,
diff --git a/src/handlers.rs b/src/handlers.rs
index 0649e5a9be88a7..e8cf62a5b86efa 100644
--- a/src/handlers.rs
+++ b/src/handlers.rs
@@ -164,7 +164,8 @@ fn test_resolve_module() {
     for &test in test_cases.iter() {
         let module_specifier = String::from(test.0);
         let containing_file = String::from(test.1);
-        let (module_name, filename) = resolve_module(&module_specifier, &containing_file).unwrap();
+        let (module_name, filename) =
+            resolve_module(&module_specifier, &containing_file).unwrap();
         assert_eq!(module_name, test.2);
         assert_eq!(filename, test.3);
     }
@@ -184,7 +185,8 @@ pub extern "C" fn handle_code_fetch(
     let result = resolve_module(&module_specifier, &containing_file);
     if result.is_err() {
         let err = result.unwrap_err();
-        let errmsg = format!("{} {} {}", err, module_specifier, containing_file);
+        let errmsg =
+            format!("{} {} {}", err, module_specifier, containing_file);
         let errmsg_c = as_cstring(&errmsg);
         unsafe { deno_reply_error(d, cmd_id, errmsg_c.as_ptr()) };
         return;
diff --git a/src/main.rs b/src/main.rs
index e1284d3039837f..efe7d86c0865b8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,8 +8,10 @@ use std::ffi::CString;
 use std::ptr;
 
 mod binding;
-use binding::{deno_delete, deno_execute, deno_handle_msg_from_js, deno_init, deno_last_exception,
-              deno_new, deno_set_flags, DenoC};
+use binding::{
+    deno_delete, deno_execute, deno_handle_msg_from_js, deno_init,
+    deno_last_exception, deno_new, deno_set_flags, DenoC,
+};
 
 // Pass the command line arguments to v8.
 // Returns a vector of command line arguments that v8 did not understand.
@@ -58,10 +60,16 @@ impl Deno {
         Deno { ptr: ptr }
     }
 
-    fn execute(&mut self, js_filename: &str, js_source: &str) -> Result<(), DenoException> {
+    fn execute(
+        &mut self,
+        js_filename: &str,
+        js_source: &str,
+    ) -> Result<(), DenoException> {
         let filename = CString::new(js_filename).unwrap();
         let source = CString::new(js_source).unwrap();
-        let r = unsafe { deno_execute(self.ptr, filename.as_ptr(), source.as_ptr()) };
+        let r = unsafe {
+            deno_execute(self.ptr, filename.as_ptr(), source.as_ptr())
+        };
         if r == 0 {
             let ptr = unsafe { deno_last_exception(self.ptr) };
             let cstr = unsafe { CStr::from_ptr(ptr) };
diff --git a/tools/format.py b/tools/format.py
index fc11ced4d4442a..cb3b15a7e4544c 100755
--- a/tools/format.py
+++ b/tools/format.py
@@ -8,6 +8,8 @@
 third_party_path = os.path.join(root_path, "third_party")
 prettier = os.path.join(third_party_path, "node_modules", "prettier",
                         "bin-prettier.js")
+tools_path = os.path.join(root_path, "tools")
+rustfmt_config = os.path.join(tools_path, "rustfmt.toml")
 
 os.chdir(root_path)
 # TODO(ry) Install clang-format in third_party.
@@ -24,5 +26,7 @@
 rustfmt_extra_args = []
 if 'RUSTFMT_FLAGS' in os.environ:
     rustfmt_extra_args += os.environ['RUSTFMT_FLAGS'].split()
-run(["rustfmt", "--write-mode", "overwrite"] + rustfmt_extra_args +
-    glob("src/*.rs"))
+run([
+    "rustfmt", "--config-path", rustfmt_config, "--error-on-unformatted",
+    "--write-mode", "overwrite"
+] + rustfmt_extra_args + glob("src/*.rs"))
diff --git a/tools/rustfmt.toml b/tools/rustfmt.toml
new file mode 100644
index 00000000000000..df99c69198f581
--- /dev/null
+++ b/tools/rustfmt.toml
@@ -0,0 +1 @@
+max_width = 80