diff --git a/message.go b/message.go
index f37e0e3..9942f06 100644
--- a/message.go
+++ b/message.go
@@ -6,7 +6,15 @@ import (
 )
 
 func (m *OSCMessage) ToBytes() ([]byte, error) {
-	//TODO(jwetzell): add error handling
+
+	if len(m.Address) == 0 {
+		return nil, errors.New("OSC Message must have an address")
+	}
+
+	if m.Address[0] != '/' {
+		return nil, errors.New("OSC Message address must start with /")
+	}
+
 	oscBuffer := []byte{}
 
 	oscBuffer = append(oscBuffer, stringToOSCBytes(m.Address)...)
@@ -18,7 +26,6 @@ func (m *OSCMessage) ToBytes() ([]byte, error) {
 	for _, arg := range m.Args {
 		sb.WriteString(arg.Type)
 	}
-
 	oscBuffer = append(oscBuffer, stringToOSCBytes(sb.String())...)
 	argsBuffer, err := argsToBuffer(m.Args)
 	if err != nil {
diff --git a/message_test.go b/message_test.go
index e163f0e..5000488 100644
--- a/message_test.go
+++ b/message_test.go
@@ -142,6 +142,47 @@ func TestGoodOSCMessageEncoding(t *testing.T) {
 
 }
 
+func TestBadOSCMessageEncoding(t *testing.T) {
+	testCases := []struct {
+		name        string
+		message     *OSCMessage
+		errorString string
+	}{
+		{
+			name:        "empty message",
+			message:     &OSCMessage{},
+			errorString: "OSC Message must have an address",
+		},
+		{
+			name:        "address does not start with /",
+			message:     &OSCMessage{Address: "hello"},
+			errorString: "OSC Message address must start with /",
+		},
+		{
+			name: "arg with unsupported type",
+			message: &OSCMessage{
+				Address: "/hello",
+				Args:    []OSCArg{{Type: "x", Value: "unsupported"}},
+			},
+			errorString: "unsupported OSC argument type: x",
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			got, err := testCase.message.ToBytes()
+
+			if err == nil {
+				t.Fatalf("OSCMessage.ToBytes() expected to fail but got: %+v", got)
+			}
+
+			if err.Error() != testCase.errorString {
+				t.Fatalf("OSCMessage.ToBytes() got error '%s', expected '%s'", err.Error(), testCase.errorString)
+			}
+		})
+	}
+}
+
 func TestGoodOSCMessageDecoding(t *testing.T) {
 	testCases := []struct {
 		name     string
diff --git a/osc.go b/osc.go
index e0be749..4e403cd 100644
--- a/osc.go
+++ b/osc.go
@@ -240,7 +240,7 @@ func argsToBuffer(args []OSCArg) ([]byte, error) {
 				fmt.Println("OSC arg had float type but non-float value.")
 			}
 		default:
-			fmt.Printf("unhandled osc type: %s.\n", oscType)
+			return nil, fmt.Errorf("unsupported OSC argument type: %s", oscType)
 		}
 	}
 	return argBuffers, nil