diff --git a/internal/command/command.go b/internal/command/command.go
index 65a3781..14d0c9e 100644
--- a/internal/command/command.go
+++ b/internal/command/command.go
@@ -1,32 +1,47 @@
+/*
+© Copyright IBM Corporation 2017
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package command contains code to run external commands
 package command
 
 import (
 	"os/exec"
 	"runtime"
-
-	"golang.org/x/sys/unix"
+	"syscall"
 )
 
 // Run runs an OS command.  On Linux it waits for the command to
 // complete and returns the exit status (return code).
+// Do not use this function to run shell built-ins (like "cd"), because
+// the error handling works differently
 func Run(name string, arg ...string) (string, int, error) {
 	cmd := exec.Command(name, arg...)
 	// Run the command and wait for completion
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		var rc int
-		// Only works on Linux
-		if runtime.GOOS == "linux" {
-			var ws unix.WaitStatus
-			unix.Wait4(cmd.Process.Pid, &ws, 0, nil)
-			rc = ws.ExitStatus()
-		} else {
-			rc = -1
+		// Assert that this is an ExitError
+		exiterr, ok := err.(*exec.ExitError)
+		// If the type assertion was correct, and we're on Linux
+		if ok && runtime.GOOS == "linux" {
+			status, ok := exiterr.Sys().(syscall.WaitStatus)
+			if ok {
+				return string(out), status.ExitStatus(), err
+			}
 		}
-		if rc == 0 {
-			return string(out), rc, nil
-		}
-		return string(out), rc, err
+		return string(out), -1, err
 	}
 	return string(out), 0, nil
 }
diff --git a/internal/command/command_test.go b/internal/command/command_test.go
new file mode 100644
index 0000000..ccd5c57
--- /dev/null
+++ b/internal/command/command_test.go
@@ -0,0 +1,47 @@
+/*
+© Copyright IBM Corporation 2017
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+package command
+
+import (
+	"runtime"
+	"testing"
+)
+
+var commandTests = []struct {
+	name string
+	arg  []string
+	rc   int
+}{
+	{"ls", []string{}, 0},
+	{"ls", []string{"madeup"}, 2},
+	{"bash", []string{"-c", "exit 99"}, 99},
+}
+
+func TestRun(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("Skipping tests for package which only works on Linux")
+	}
+	for _, table := range commandTests {
+		arg := table.arg
+		_, rc, err := Run(table.name, arg...)
+		if rc != table.rc {
+			t.Errorf("Run(%v,%v) - expected %v, got %v", table.name, table.arg, table.rc, rc)
+		}
+		if rc != 0 && err == nil {
+			t.Errorf("Run(%v,%v) - expected error for non-zero return code (rc=%v)", table.name, table.arg, rc)
+		}
+	}
+}