diff --git a/ca-store-generator.js b/ca-store-generator.js
index fad899e..da803d2 100644
--- a/ca-store-generator.js
+++ b/ca-store-generator.js
@@ -200,7 +200,7 @@ function run(filename) {
 
     if (!fs.existsSync(outputPemsDir)) {
       fs.mkdirSync(outputPemsDir);
-    } 
+    }
 
     console.info("Loading latest certificates from " + CERTDB_URL);
     request.get(CERTDB_URL, function (error, response, body) {
@@ -217,6 +217,12 @@ function run(filename) {
         return;
       }
 
+      if (response.headers['content-type'] !== 'text/plain') {
+        console.error("Fetching failed with incorrect content type %s", response.headers['content-type']);
+        reject({ code: 2, error: "Fetching failed with incorrect content type " + response.headers['content-type'] });
+        return;
+      }
+
       var lines = body.split("\n")
         , certs = parseCertData(lines)
         , pemsFile = path.join(outputPemsDir, 'mozilla-certdata.txt')