diff --git a/src/command/build.rs b/src/command/build.rs
index c9ebf59..0d649e8 100644
--- a/src/command/build.rs
+++ b/src/command/build.rs
@@ -64,12 +64,15 @@ pub struct BuildOptions {
     // build_config: Option<BuildConfig>,
 }
 
-impl From<BuildOptions> for Build {
-    fn from(build_opts: BuildOptions) -> Self {
+type BuildStep = fn(&mut Build, &Step, &Logger) -> Result<(), Error>;
+
+impl Build {
+    /// Construct a build command from the given options.
+    pub fn try_from_opts(build_opts: BuildOptions) -> Result<Self, Error> {
         let crate_path = set_crate_path(build_opts.path);
-        let crate_name = manifest::get_crate_name(&crate_path).unwrap();
+        let crate_name = manifest::get_crate_name(&crate_path)?;
         // let build_config = manifest::xxx(&crate_path).xxx();
-        Build {
+        Ok(Build {
             crate_path,
             scope: build_opts.scope,
             disable_dts: build_opts.disable_dts,
@@ -77,13 +80,9 @@ impl From<BuildOptions> for Build {
             debug: build_opts.debug,
             // build_config,
             crate_name,
-        }
+        })
     }
-}
-
-type BuildStep = fn(&mut Build, &Step, &Logger) -> Result<(), Error>;
 
-impl Build {
     /// Execute this `Build` command.
     pub fn run(&mut self, log: &Logger, mode: &BuildMode) -> Result<(), Error> {
         let process_steps = Build::get_process_steps(mode);
diff --git a/src/command/mod.rs b/src/command/mod.rs
index 9b20672..fe001fa 100644
--- a/src/command/mod.rs
+++ b/src/command/mod.rs
@@ -84,7 +84,7 @@ pub fn run_wasm_pack(command: Command, log: &Logger) -> result::Result<(), Error
                 "normal" => BuildMode::Normal,
                 _ => BuildMode::Normal,
             };
-            Build::from(build_opts).run(&log, &build_mode)
+            Build::try_from_opts(build_opts).and_then(|mut b| b.run(&log, &build_mode))
         }
         Command::Pack { path } => {
             info!(&log, "Running pack command...");
diff --git a/src/logger.rs b/src/logger.rs
index d100ccf..0f272a9 100644
--- a/src/logger.rs
+++ b/src/logger.rs
@@ -11,7 +11,10 @@ use std::path::PathBuf;
 /// Create the logger for wasm-pack that will output any info warning or errors we encounter
 pub fn new(cmd: &Command, verbosity: u8) -> Result<Logger, Error> {
     let log_path = log_file_path(&cmd);
-    let file = OpenOptions::new().create(true).append(true).open(log_path)?;
+    let file = OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(log_path)?;
 
     let decorator = PlainDecorator::new(file);
     let drain = FullFormat::new(decorator).build().fuse();
diff --git a/src/manifest.rs b/src/manifest.rs
index 2cc3919..81d464f 100644
--- a/src/manifest.rs
+++ b/src/manifest.rs
@@ -68,6 +68,12 @@ struct Repository {
 
 fn read_cargo_toml(path: &Path) -> Result<CargoManifest, Error> {
     let manifest_path = path.join("Cargo.toml");
+    if !manifest_path.is_file() {
+        return Error::crate_config(&format!(
+            "Crate directory is missing a `Cargo.toml` file; is `{}` the wrong directory?",
+            path.display()
+        )).map(|_| unreachable!());
+    }
     let mut cargo_file = File::open(manifest_path)?;
     let mut cargo_contents = String::new();
     cargo_file.read_to_string(&mut cargo_contents)?;
diff --git a/tests/all/build.rs b/tests/all/build.rs
new file mode 100644
index 0000000..ea821b5
--- /dev/null
+++ b/tests/all/build.rs
@@ -0,0 +1,21 @@
+use structopt::StructOpt;
+use utils;
+use wasm_pack::{command, logger, Cli};
+
+#[test]
+fn build_in_non_crate_directory_doesnt_panic() {
+    let fixture = utils::fixture::fixture("tests/fixtures/not-a-crate");
+    let cli = Cli::from_iter_safe(vec![
+        "wasm-pack",
+        "build",
+        &fixture.path.display().to_string(),
+    ]).unwrap();
+    let logger = logger::new(&cli.cmd, cli.verbosity).unwrap();
+    let result = command::run_wasm_pack(cli.cmd, &logger);
+    assert!(
+        result.is_err(),
+        "running wasm-pack in a non-crate directory should fail, but it should not panic"
+    );
+    let err_msg = result.unwrap_err().to_string();
+    assert!(err_msg.contains("missing a `Cargo.toml`"));
+}
diff --git a/tests/all/main.rs b/tests/all/main.rs
index 998588e..57f8885 100644
--- a/tests/all/main.rs
+++ b/tests/all/main.rs
@@ -3,9 +3,11 @@ extern crate failure;
 #[macro_use]
 extern crate serde_derive;
 extern crate serde_json;
+extern crate structopt;
 extern crate tempfile;
 extern crate wasm_pack;
 
+mod build;
 mod manifest;
 mod readme;
 mod utils;
diff --git a/tests/fixtures/not-a-crate/README.md b/tests/fixtures/not-a-crate/README.md
new file mode 100644
index 0000000..ea36f59
--- /dev/null
+++ b/tests/fixtures/not-a-crate/README.md
@@ -0,0 +1 @@
+This is not a Rust crate!