diff --git a/lib/PayPal/Core/PayPalHttpConfig.php b/lib/PayPal/Core/PayPalHttpConfig.php
index 8a2b2a3..0afabc3 100644
--- a/lib/PayPal/Core/PayPalHttpConfig.php
+++ b/lib/PayPal/Core/PayPalHttpConfig.php
@@ -64,7 +64,7 @@ class PayPalHttpConfig
         // Update the Cipher List based on OpenSSL or NSS settings
         $curl = curl_version();
         $sslVersion = isset($curl['ssl_version']) ? $curl['ssl_version'] : '';
-        if (substr_compare($sslVersion, "NSS/", 0, strlen("NSS/")) === 0) {
+        if($sslVersion && substr_compare($sslVersion, "NSS/", 0, strlen("NSS/")) === 0) {
             //Remove the Cipher List for NSS
             $this->removeCurlOption(CURLOPT_SSL_CIPHER_LIST);
         }