diff --git a/Cargo.toml b/Cargo.toml
index 10b1f72..d7883cb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,6 +9,7 @@ license = "MIT OR Apache-2.0"
 name = "xargo"
 repository = "https://github.com/japaric/xargo"
 version = "0.3.18"
+default-run = "xargo"
 
 [dependencies]
 error-chain = "0.7.2"
diff --git a/README.md b/README.md
index 65facb0..6402e39 100644
--- a/README.md
+++ b/README.md
@@ -309,6 +309,18 @@ git = "https://github.com/japaric/steed"
 stage = 2
 ```
 
+## Check-only sysroot build
+
+Xargo supports performing a 'check build' of the syroot
+via the `xargo-check` command. This command is invoked exactly
+like `xargo`, but will invoke `cargo check` instead of `cargo build`
+when building the sysroot.
+
+This is only useful for very specialized applicationsm like Miri.
+The resulting libstd will *not* be useable in a normal build, since codegen
+will not be performed. You should almost always run `xargo check` (note the space),
+which will perform a normal sysroot build, followed by a 'check' build of *your application*
+
 ## Caveats / gotchas
 
 - Xargo won't build a sysroot when used with stable or beta Rust. This is
diff --git a/ci/script.sh b/ci/script.sh
index edee9f0..83fe957 100644
--- a/ci/script.sh
+++ b/ci/script.sh
@@ -3,8 +3,14 @@ set -euxo pipefail
 beginswith() { case $2 in "$1"*) true;; *) false;; esac; }
 
 main() {
+    # We test against Cargo versions that don't support 'default-run'
+    # As a workaround, we remove 'default-run' from the Cargo.toml
+    # on CI
+    # Unfortunately, we can't use 'sed -i', as this doesn't work on OS X
+    sed 's/default-run = "xargo"//g' Cargo.toml > Cargo.toml.new
+    mv Cargo.toml.new Cargo.toml
     cross build --target $TARGET --locked
-    cross run --target $TARGET -- -V
+    cross run --bin xargo --target $TARGET -- -V
 
     if beginswith nightly $TRAVIS_RUST_VERSION; then
         cargo test --features dev --target $TARGET
diff --git a/src/bin/xargo-check.rs b/src/bin/xargo-check.rs
new file mode 100644
index 0000000..619c12e
--- /dev/null
+++ b/src/bin/xargo-check.rs
@@ -0,0 +1,3 @@
+fn main() {
+    xargo::main_inner(xargo::XargoMode::Check);
+}
diff --git a/src/bin/xargo.rs b/src/bin/xargo.rs
new file mode 100644
index 0000000..663421e
--- /dev/null
+++ b/src/bin/xargo.rs
@@ -0,0 +1,3 @@
+fn main() {
+    xargo::main_inner(xargo::XargoMode::Build);
+}
diff --git a/src/cargo.rs b/src/cargo.rs
index b347bce..d7fbdcf 100644
--- a/src/cargo.rs
+++ b/src/cargo.rs
@@ -10,6 +10,7 @@ use cli::Args;
 use errors::*;
 use extensions::CommandExt;
 use util;
+use sysroot::XargoMode;
 use xargo::Home;
 
 pub struct Rustflags {
@@ -247,10 +248,15 @@ impl Root {
     }
 }
 
-pub fn root() -> Result<Option<Root>> {
+pub fn root(mode: XargoMode) -> Result<Option<Root>> {
+    // Don't require a 'Cargo.toml' to exist when 'xargo-check' is used
+    let name = match mode {
+        XargoMode::Build => "Cargo.toml",
+        XargoMode::Check => "Xargo.toml"
+    };
     let cd = env::current_dir().chain_err(|| "couldn't get the current directory")?;
 
-    Ok(util::search(&cd, "Cargo.toml").map(|p| Root { path: p.to_owned() }))
+    Ok(util::search(&cd, name).map(|p| Root { path: p.to_owned() }))
 }
 
 #[derive(Clone, Copy, PartialEq)]
diff --git a/src/main.rs b/src/lib.rs
similarity index 84%
rename from src/main.rs
rename to src/lib.rs
index 908336d..883bb67 100644
--- a/src/main.rs
+++ b/src/lib.rs
@@ -33,6 +33,8 @@ mod sysroot;
 mod util;
 mod xargo;
 
+pub use sysroot::XargoMode;
+
 // We use a different sysroot for Native compilation to avoid file locking
 //
 // Cross compilation requires `lib/rustlib/$HOST` to match `rustc`'s sysroot,
@@ -72,12 +74,12 @@ impl CompilationMode {
     }
 }
 
-pub fn main() {
+pub fn main_inner(xargo_mode: XargoMode) {
     fn show_backtrace() -> bool {
         env::var("RUST_BACKTRACE").as_ref().map(|s| &s[..]) == Ok("1")
     }
 
-    match run() {
+    match run(xargo_mode) {
         Err(e) => {
             let stderr = io::stderr();
             let mut stderr = stderr.lock();
@@ -98,13 +100,14 @@ pub fn main() {
 
             process::exit(1)
         }
-        Ok(status) => if !status.success() {
+        Ok(Some(status)) => if !status.success() {
             process::exit(status.code().unwrap_or(1))
         },
+        Ok(None) => {}
     }
 }
 
-fn run() -> Result<ExitStatus> {
+fn run(cargo_mode: XargoMode) -> Result<Option<ExitStatus>> {
     let args = cli::args();
     let verbose = args.verbose();
 
@@ -112,7 +115,7 @@ fn run() -> Result<ExitStatus> {
 
     if let Some(sc) = args.subcommand() {
         if !sc.needs_sysroot() {
-            return cargo::run(&args, verbose);
+            return cargo::run(&args, verbose).map(Some);
         }
     } else if args.version() {
         writeln!(
@@ -121,13 +124,13 @@ fn run() -> Result<ExitStatus> {
             include_str!(concat!(env!("OUT_DIR"), "/commit-info.txt"))
         ).ok();
 
-        return cargo::run(&args, verbose);
+        return cargo::run(&args, verbose).map(Some);
     }
 
     let cd = CurrentDirectory::get()?;
 
     let config = cargo::config()?;
-    if let Some(root) = cargo::root()? {
+    if let Some(root) = cargo::root(cargo_mode)? {
         // We can't build sysroot with stable or beta due to unstable features
         let sysroot = rustc::sysroot(verbose)?;
         let src = match meta.channel {
@@ -147,7 +150,7 @@ fn run() -> Result<ExitStatus> {
                      Switch to nightly.",
                     meta.channel
                 ).ok();
-                return cargo::run(&args, verbose);
+                return cargo::run(&args, verbose).map(Some);
             }
         };
 
@@ -187,21 +190,27 @@ fn run() -> Result<ExitStatus> {
                 &src,
                 &sysroot,
                 verbose,
-                args.message_format()
+                args.message_format(),
+                cargo_mode,
             )?;
-            return xargo::run(
-                &args,
-                &cmode,
-                rustflags,
-                &home,
-                &meta,
-                config.as_ref(),
-                verbose,
-            );
+
+            if args.subcommand().is_some() || cargo_mode == XargoMode::Build {
+                return xargo::run(
+                    &args,
+                    &cmode,
+                    rustflags,
+                    &home,
+                    &meta,
+                    config.as_ref(),
+                    verbose,
+                ).map(Some);
+            } else {
+                return Ok(None)
+            }
         }
     }
 
-    cargo::run(&args, verbose)
+    cargo::run(&args, verbose).map(Some)
 }
 
 pub struct CurrentDirectory {
diff --git a/src/sysroot.rs b/src/sysroot.rs
index e8a2715..418b437 100644
--- a/src/sysroot.rs
+++ b/src/sysroot.rs
@@ -31,14 +31,15 @@ fn profile() -> &'static str {
 fn build(
     cmode: &CompilationMode,
     blueprint: Blueprint,
-    ctoml: &cargo::Toml,
+    ctoml: &Option<cargo::Toml>,
     home: &Home,
     rustflags: &Rustflags,
     src: &Src,
     sysroot: &Sysroot,
     hash: u64,
     verbose: bool,
-    message_format: Option<&str>
+    message_format: Option<&str>,
+    cargo_mode: XargoMode,
 ) -> Result<()> {
     const TOML: &'static str = r#"
 [package]
@@ -96,8 +97,10 @@ version = "0.0.0"
             stoml.push_str(&Value::Table(map).to_string());
         }
 
-        if let Some(profile) = ctoml.profile() {
-            stoml.push_str(&profile.to_string())
+        if let Some(ctoml) = ctoml {
+            if let Some(profile) = ctoml.profile() {
+                stoml.push_str(&profile.to_string())
+            }
         }
 
         // rust-src comes with a lockfile for libstd. Use it.
@@ -165,7 +168,10 @@ version = "0.0.0"
                 }
             }
 
-            cmd.arg("build");
+            match cargo_mode {
+                XargoMode::Build => cmd.arg("build"),
+                XargoMode::Check => cmd.arg("check")
+            };
 
             match () {
                 #[cfg(feature = "dev")]
@@ -234,7 +240,7 @@ fn hash(
     cmode: &CompilationMode,
     blueprint: &Blueprint,
     rustflags: &Rustflags,
-    ctoml: &cargo::Toml,
+    ctoml: &Option<cargo::Toml>,
     meta: &VersionMeta,
 ) -> Result<u64> {
     let mut hasher = DefaultHasher::new();
@@ -245,8 +251,10 @@ fn hash(
 
     cmode.hash(&mut hasher)?;
 
-    if let Some(profile) = ctoml.profile() {
-        profile.hash(&mut hasher);
+    if let Some(ctoml) = ctoml {
+        if let Some(profile) = ctoml.profile() {
+            profile.hash(&mut hasher);
+        }
     }
 
     if let Some(ref hash) = meta.commit_hash {
@@ -265,9 +273,20 @@ pub fn update(
     src: &Src,
     sysroot: &Sysroot,
     verbose: bool,
-    message_format: Option<&str>
+    message_format: Option<&str>,
+    cargo_mode: XargoMode,
 ) -> Result<()> {
-    let ctoml = cargo::toml(root)?;
+    let ctoml = match cargo_mode {
+        XargoMode::Build => Some(cargo::toml(root)?),
+        XargoMode::Check => {
+            if root.path().join("Cargo.toml").exists() {
+                Some(cargo::toml(root)?)
+            } else {
+                None
+            }
+        }
+    };
+
     let (xtoml_parent, xtoml) = xargo::toml(root)?;
 
     // As paths in the 'Xargo.toml' can be relative to the directory containing
@@ -292,6 +311,7 @@ pub fn update(
             hash,
             verbose,
             message_format,
+            cargo_mode,
         )?;
     }
 
@@ -344,6 +364,14 @@ pub struct Stage {
     patch: Table,
 }
 
+/// Which mode to invoke `cargo` in when building the sysroot
+/// Can be either `cargo build` or `cargo check`
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum XargoMode {
+    Build,
+    Check,
+}
+
 /// A sysroot that will be built in "stages"
 #[derive(Debug)]
 pub struct Blueprint {
diff --git a/tests/smoke.rs b/tests/smoke.rs
index 7610869..0c72e3c 100644
--- a/tests/smoke.rs
+++ b/tests/smoke.rs
@@ -121,6 +121,14 @@ fn xargo() -> Result<Command> {
     Ok(Command::new(p))
 }
 
+fn xargo_check() -> Result<Command> {
+    let mut p = env::current_exe().chain_err(|| "couldn't get path to current executable")?;
+    p.pop();
+    p.pop();
+    p.push("xargo-check");
+    Ok(Command::new(p))
+}
+
 trait CommandExt {
     fn run(&mut self) -> Result<()>;
     fn run_and_get_stderr(&mut self) -> Result<String>;
@@ -254,6 +262,7 @@ impl Project {
         Ok(())
     }
 
+
     /// Adds a `Xargo.toml` to the project
     fn xargo_toml(&self, toml: &str) -> Result<()> {
         write(&self.td.path().join("Xargo.toml"), false, toml)
@@ -336,6 +345,18 @@ impl HProject {
     fn xargo_toml(&self, toml: &str) -> Result<()> {
         write(&self.td.path().join("Xargo.toml"), false, toml)
     }
+
+    /// Runs `xargo-check` with the specified subcommand
+    fn xargo_check_subcommand(&self, subcommand: Option<&str>) -> Result<String> {
+        let mut cmd = xargo_check()?;
+        if let Some(subcommand) = subcommand {
+            cmd.args(&[subcommand]);
+        }
+        cmd
+            .current_dir(self.td.path())
+            .run_and_get_stderr()
+    }
+
 }
 
 impl Drop for HProject {
@@ -887,3 +908,33 @@ tag = "1.0.25"
         run!()
     }
 }
+
+#[cfg(feature = "dev")]
+#[test]
+fn cargo_check_check() {
+    fn run() -> Result<()> {
+        let project = HProject::new(false)?;
+        project.xargo_check_subcommand(Some("check"))?;
+
+        Ok(())
+    }
+    run!()
+}
+
+#[cfg(feature = "dev")]
+#[test]
+fn cargo_check_check_no_ctoml() {
+    fn run() -> Result<()> {
+        let project = HProject::new(false)?;
+        // Make sure that 'Xargo.toml` exists
+        project.xargo_toml("")?;
+        std::fs::remove_file(project.td.path().join("Cargo.toml"))
+            .chain_err(|| format!("Could not remove Cargo.toml"))?;
+
+        let stderr = project.xargo_check_subcommand(None)?;
+        assert!(stderr.contains("Checking core"));
+
+        Ok(())
+    }
+    run!()
+}