diff --git a/helper/communicator/config.go b/helper/communicator/config.go
index a2719db13..a2d93a480 100644
--- a/helper/communicator/config.go
+++ b/helper/communicator/config.go
@@ -2,6 +2,8 @@ package communicator
 
 import (
 	"errors"
+	"fmt"
+	"os"
 	"time"
 
 	"github.com/mitchellh/packer/template/interpolate"
@@ -39,6 +41,16 @@ func (c *Config) Prepare(ctx *interpolate.Context) []error {
 		if c.SSHUsername == "" {
 			errs = append(errs, errors.New("An ssh_username must be specified"))
 		}
+
+		if c.SSHPrivateKey != "" {
+			if _, err := os.Stat(c.SSHPrivateKey); err != nil {
+				errs = append(errs, fmt.Errorf(
+					"ssh_private_key_file is invalid: %s", err))
+			} else if _, err := SSHFileSigner(c.SSHPrivateKey); err != nil {
+				errs = append(errs, fmt.Errorf(
+					"ssh_private_key_file is invalid: %s", err))
+			}
+		}
 	}
 
 	return errs
diff --git a/helper/communicator/ssh.go b/helper/communicator/ssh.go
new file mode 100644
index 000000000..831d620bc
--- /dev/null
+++ b/helper/communicator/ssh.go
@@ -0,0 +1,44 @@
+package communicator
+
+import (
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// SSHFileSigner returns an ssh.Signer for a key file.
+func SSHFileSigner(path string) (ssh.Signer, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	keyBytes, err := ioutil.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	// We parse the private key on our own first so that we can
+	// show a nicer error if the private key has a password.
+	block, _ := pem.Decode(keyBytes)
+	if block == nil {
+		return nil, fmt.Errorf(
+			"Failed to read key '%s': no key found", path)
+	}
+	if block.Headers["Proc-Type"] == "4,ENCRYPTED" {
+		return nil, fmt.Errorf(
+			"Failed to read key '%s': password protected keys are\n"+
+				"not supported. Please decrypt the key prior to use.", path)
+	}
+
+	signer, err := ssh.ParsePrivateKey(keyBytes)
+	if err != nil {
+		return nil, fmt.Errorf("Error setting up SSH config: %s", err)
+	}
+
+	return signer, nil
+}