diff --git a/src/NexmoMessage.php b/src/NexmoMessage.php
index 1c637db..a290b8b 100644
--- a/src/NexmoMessage.php
+++ b/src/NexmoMessage.php
@@ -83,10 +83,10 @@ function sendText ( $to, $from, $message, $unicode=null ) {
 			return false;
 		}
 		
-		if ($unicode === null) {
-			$containsUnicode = max(array_map('ord', str_split($message))) > 127;
+		if (!is_null($unicode)) {
+			$unicode = (boolean) $unicode;
 		} else {
-			$containsUnicode = (bool)$unicode;
+			$unicode = !$this->stringIsGSM0338($message);
 		}
 		
 		// Make sure $from is valid
@@ -101,7 +101,7 @@ function sendText ( $to, $from, $message, $unicode=null ) {
 			'from' => $from,
 			'to' => $to,
 			'text' => $message,
-			'type' => $containsUnicode ? 'unicode' : 'text'
+			'type' => $unicode ? 'unicode' : 'text'
 		);
 		return $this->sendRequest ( $post );
 		
@@ -433,4 +433,33 @@ public function reply ($message) {
 		return $this->sendText($this->from, $this->to, $message);
 	}
 
+	public function stringIsGSM0338($str) {
+
+		    $gsm0338 = array(
+		        '@','Δ',' ','0','¡','P','¿','p',
+		        '£','_','!','1','A','Q','a','q',
+		        '$','Φ','"','2','B','R','b','r',
+		        '¥','Γ','#','3','C','S','c','s',
+		        'è','Λ','¤','4','D','T','d','t',
+		        'é','Ω','%','5','E','U','e','u',
+		        'ù','Π','&','6','F','V','f','v',
+		        'ì','Ψ','\'','7','G','W','g','w',
+		        'ò','Σ','(','8','H','X','h','x',
+		        'Ç','Θ',')','9','I','Y','i','y',
+		        "\n",'Ξ','*',':','J','Z','j','z',
+		        'Ø',"\x1B",'+',';','K','Ä','k','ä',
+		        'ø','Æ',',','<','L','Ö','l','ö',
+		        "\r",'æ','-','=','M','Ñ','m','ñ',
+		        'Å','ß','.','>','N','Ü','n','ü',
+		        'å','É','/','?','O','§','o','à'
+		     );
+
+		    $len = mb_strlen($str, 'UTF-8');
+
+		    for( $i=0; $i < $len; $i++)
+		        if (!in_array(mb_substr($str,$i,1,'UTF-8'), $gsm0338))
+		            return false;
+
+		    return true;
+		}
 }