diff --git a/QuickChart.php b/QuickChart.php
index 21f95d3..88eadd8 100644
--- a/QuickChart.php
+++ b/QuickChart.php
@@ -146,11 +146,39 @@ function toBinary() {
     curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type:application/json'));
     curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
     $result = curl_exec($ch);
+    $httpStatusCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
+
     if ($result === false) {
-      throw new ErrorException(curl_error($ch));
+      $error = curl_error($ch);
+      curl_close($ch);
+      throw new Exception("Curl error: $error");
     }
+
     curl_close($ch);
-    return $result;
+
+    if ($httpStatusCode >= 200 && $httpStatusCode < 300) {
+      return $result;
+    }
+
+    // Parse response headers
+    $responseHeaders = [];
+    $headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
+    $headerStr = substr($result, 0, $headerSize);
+    foreach (explode("\r\n", $headerStr) as $i => $line) {
+      if ($i === 0) {
+        $responseHeaders['http_code'] = $line;
+      } else {
+        list($key, $value) = explode(': ', $line);
+        $responseHeaders[$key] = $value;
+      }
+    }
+
+    $errorHeader = isset($responseHeaders['X-quickchart-error']) ? $responseHeaders['X-quickchart-error'] : null;
+    if ($errorHeader) {
+      throw new Exception("QuickChart API returned an error with status code: $httpStatusCode. Error: $errorHeader");
+    }
+
+    throw new Exception("QuickChart API returned an error with status code: $httpStatusCode. Response: $result");
   }
 
   function toFile($path) {