diff --git a/signal_request.go b/signal_request.go
index 4e7dde1e..9cfd8395 100644
--- a/signal_request.go
+++ b/signal_request.go
@@ -69,6 +69,14 @@ func (b *signalBuilder) QueryParam(queryParam map[string]string) *signalBuilder
 	return b
 }
 
+// CustomMessageType sets the User-specified message type string - limited by 3-50 case-sensitive alphanumeric characters
+// with only `-` and `_` special characters allowed.
+func (b *signalBuilder) CustomMessageType(messageType string) *signalBuilder {
+    b.opts.CustomMessageType = messageType
+
+    return b
+}
+
 // Execute runs the Signal request.
 func (b *signalBuilder) Execute() (*SignalResponse, StatusResponse, error) {
 	rawJSON, status, err := executeRequest(b.opts)
@@ -86,6 +94,25 @@ type signalOpts struct {
 	UsePost    bool
 	QueryParam map[string]string
 	Transport  http.RoundTripper
+    CustomMessageType string
+}
+
+func (o *signalOpts) isCustomMessageTypeCorrect() bool {
+    if len(o.CustomMessageType) == 0 {
+        return true
+    }
+
+    if len(o.CustomMessageType) < 3 || len(o.CustomMessageType) > 50 {
+        return false
+    }
+
+    for _, c := range o.CustomMessageType {
+        if !('a' <= c && 'z' >= c) && !('A' <= c && 'Z' >= c) && c != '-' && c != '_' {
+            return false
+        }
+    }
+
+    return true
 }
 
 func (o *signalOpts) validate() error {
@@ -97,6 +124,10 @@ func (o *signalOpts) validate() error {
 		return newValidationError(o, StrMissingPubKey)
 	}
 
+    if !o.isCustomMessageTypeCorrect() {
+        return newValidationError(o, StrInvalidCustomMessageType)
+    }
+
 	return nil
 }
 
@@ -130,6 +161,10 @@ func (o *signalOpts) buildQuery() (*url.Values, error) {
 
 	SetQueryParam(q, o.QueryParam)
 
+    if len(o.CustomMessageType) > 0 {
+        q.Set("custom_message_type", o.CustomMessageType)
+    }
+
 	return q, nil
 }
 
diff --git a/signal_request_test.go b/signal_request_test.go
index faea4ea6..a01f8c03 100644
--- a/signal_request_test.go
+++ b/signal_request_test.go
@@ -26,6 +26,7 @@ func AssertSuccessSignalGet(t *testing.T, channel string, checkQueryParam bool)
 	opts.Channel = channel
 	opts.Message = msgMap
 	opts.QueryParam = queryParam
+    opts.CustomMessageType = "custom"
 
 	path, err := opts.buildPath()
 	assert.Nil(err)
@@ -43,8 +44,8 @@ func AssertSuccessSignalGet(t *testing.T, channel string, checkQueryParam bool)
 		u, _ := opts.buildQuery()
 		assert.Equal("v1", u.Get("q1"))
 		assert.Equal("v2", u.Get("q2"))
+        assert.Equal("custom", u.Get("custom_message_type"))
 	}
-
 }
 
 func TestSignalPath(t *testing.T) {
@@ -144,3 +145,15 @@ func TestSignalResponseValuePass(t *testing.T) {
 	_, _, err := newSignalResponse(jsonBytes, opts, StatusResponse{})
 	assert.Nil(err)
 }
+
+func TestSignalCustomMessageTypeValidation(t *testing.T) {
+    assert := assert.New(t)
+    pn := NewPubNub(NewDemoConfig())
+    opts := newSignalOpts(pn, pn.ctx)
+    opts.CustomMessageType = "custom-message_type"
+    assert.True(opts.isCustomMessageTypeCorrect())
+    opts.CustomMessageType = "a"
+    assert.False(opts.isCustomMessageTypeCorrect())
+    opts.CustomMessageType = "!@#$%^&*("
+    assert.False(opts.isCustomMessageTypeCorrect())
+}