diff --git a/composer.json b/composer.json
index a1d5007..b9b5342 100644
--- a/composer.json
+++ b/composer.json
@@ -2,10 +2,10 @@
     "name": "payvision/payvision-sdk-php",
     "description": "Payvision PHP SDK",
     "type": "library",
-    "version": "5.1.2",
+    "version": "6.0.0",
     "license": "MIT",
     "require": {
-        "php": "^7.2.5|^7.3",
+        "php": "~7.1.3||~7.2.5||~7.3.0||~7.4.0",
         "ext-simplexml": "*",
         "ext-json": "*",
         "ext-curl": "*",
@@ -23,9 +23,9 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.5",
+        "phpunit/phpunit": "^7.5",
         "dealerdirect/phpcodesniffer-composer-installer": "^0.7.0",
-        "object-calisthenics/phpcs-calisthenics-rules": "^3.8",
+        "object-calisthenics/phpcs-calisthenics-rules": "^3.0",
         "phpcompatibility/php-compatibility": "^9.3",
         "slevomat/coding-standard": "^6.3",
         "squizlabs/php_codesniffer": "^3.5"
diff --git a/phpcs.xml b/phpcs.xml
index ad8aa04..2f2e0a4 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -30,7 +30,7 @@
 
     <!-- PHP compatibility -->
     <rule ref="PHPCompatibility"/>
-    <config name="testVersion" value="7.2-"/>
+    <config name="testVersion" value="7.1-"/>
 
     <!-- Extra rules -->
     <rule ref="Generic.Arrays.ArrayIndent"/>
diff --git a/src/Infrastructure/ApiConnection.php b/src/Infrastructure/ApiConnection.php
index e041ce1..a56d53d 100644
--- a/src/Infrastructure/ApiConnection.php
+++ b/src/Infrastructure/ApiConnection.php
@@ -17,6 +17,7 @@
 use Payvision\SDK\Exception\Api\ErrorResponse;
 use Payvision\SDK\Exception\ApiException;
 use Payvision\SDK\Exception\BuilderException;
+use Psr\Http\Message\ResponseInterface;
 use ReflectionException;
 
 class ApiConnection implements Connection
@@ -107,6 +108,7 @@ public function executeAndReturnArray(Request $request): array
      * @param RequestHeaderCollection $requestHeaderCollection
      * @return array
      * @throws ApiException
+     * @throws ErrorResponse
      */
     private function get(Request $request, RequestHeaderCollection $requestHeaderCollection): array
     {
@@ -116,19 +118,7 @@ private function get(Request $request, RequestHeaderCollection $requestHeaderCol
         );
 
         $this->lastJsonRequest = $request->getPathParams();
-        $this->lastStatusCode = $guzzleResponse->getStatusCode();
-        $contents = $guzzleResponse->getBody()->getContents();
-        $json = \json_decode($contents, true);
-
-        if (!\is_array($json)) {
-            $this->logDebugData($this->lastJsonRequest, ['_raw_response' => $contents], $requestHeaderCollection);
-            throw new ApiException(
-                \sprintf('Response is not JSON: %1$s', $contents),
-                ApiException::INVALID_RESPONSE
-            );
-        }
-
-        return $json;
+        return $this->parseJSONResponse($guzzleResponse, $requestHeaderCollection);
     }
 
     /**
@@ -136,6 +126,7 @@ private function get(Request $request, RequestHeaderCollection $requestHeaderCol
      * @param RequestHeaderCollection $requestHeaderCollection
      * @return array
      * @throws ApiException
+     * @throws ErrorResponse
      */
     private function post(Request $request, RequestHeaderCollection $requestHeaderCollection): array
     {
@@ -147,12 +138,32 @@ private function post(Request $request, RequestHeaderCollection $requestHeaderCo
         );
 
         $this->lastJsonRequest = $jsonRequest;
+        return $this->parseJSONResponse($guzzleResponse, $requestHeaderCollection);
+    }
+
+    /**
+     * @throws ApiException
+     * @throws ErrorResponse
+     */
+    private function parseJSONResponse(
+        ResponseInterface $guzzleResponse,
+        RequestHeaderCollection $requestHeaderCollection
+    ): array {
         $this->lastStatusCode = $guzzleResponse->getStatusCode();
         $contents = $guzzleResponse->getBody()->getContents();
         $json = \json_decode($contents, true);
 
         if (!\is_array($json)) {
             $this->logDebugData($this->lastJsonRequest, ['_raw_response' => $contents], $requestHeaderCollection);
+
+            if ($this->lastStatusCode >= 400) {
+                throw new ErrorResponse(
+                    $guzzleResponse,
+                    'Invalid response code received',
+                    ErrorResponse::INVALID_RESPONSE
+                );
+            }
+
             throw new ApiException(
                 \sprintf('Response is not JSON: %1$s', $contents),
                 ApiException::INVALID_RESPONSE
@@ -250,6 +261,7 @@ private function handleResponse(
      * @param Request $request
      * @param array $requestHeaders
      * @return array
+     * @throws ErrorResponse
      * @throws ApiException
      */
     private function doRequest(Request $request, array $requestHeaders = []): array