diff --git a/src/OTP/Options.php b/src/OTP/Options.php
index 7c02ca8..34544fb 100644
--- a/src/OTP/Options.php
+++ b/src/OTP/Options.php
@@ -23,7 +23,7 @@ public function otp($otp = null)
      * @param int|null $mobile - receipient's mobile number
      * @return $this
      */
-    public function to($mobile = null): self
+    public function to($mobile = null)
     {
         $this->mobile($mobile);
         return $this;
diff --git a/src/Options.php b/src/Options.php
index 7c578af..bff0c92 100644
--- a/src/Options.php
+++ b/src/Options.php
@@ -33,7 +33,7 @@ public function key($key = null)
         return $this;
     }
 
-    abstract public function to($mobile = null): self;
+    abstract public function to($mobile = null);
 
     /**
      * Set the sender of the message
diff --git a/src/SMS/Options.php b/src/SMS/Options.php
index 4798573..bd9cb9c 100644
--- a/src/SMS/Options.php
+++ b/src/SMS/Options.php
@@ -12,7 +12,7 @@ class Options extends Msg91Options
      * @param int|array|null $mobile - receipient's mobile number
      * @return $this
      */
-    public function to($mobile = null): self
+    public function to($mobile = null)
     {
         if (is_array($mobile)) {
             if (count($mobile) > 0 && is_array($mobile[0])) {