2 files changed, 13 insertions, 6 deletions
diff --git a/lib/results.js b/lib/results.js
index 043f1f9..2c89be3 100644
--- a/lib/results.js
+++ b/lib/results.js
@@ -46,11 +46,18 @@ function warning(message) {
 }
 
 function error(exception) {
-    return {
-        type: "error",
-        message: exception.message,
-        stack: exception.stack
-    };
+    if (typeof exception == 'string') {
+        return {
+            type: "error",
+            message: exception
+        };
+    } else {
+        return {
+            type: "error",
+            message: exception.message,
+            stack: exception.stack
+        };
+    }
 }
 
 function combineMessages(results) {
diff --git a/test/mammoth.tests.js b/test/mammoth.tests.js
index 1a82014..622fcbb 100644
--- a/test/mammoth.tests.js
+++ b/test/mammoth.tests.js
@@ -197,7 +197,7 @@ describe('mammoth', function() {
         var buffer = fs.readFileSync(docxPath);
         return mammoth.convertToHtml({buffer: buffer}).then(function(result) {
             assert.equal(result.value, '');
-            assert.deepEqual(result.messages, [results.warning("could not find external image 'tiny-picture.png', path of input document is unknown")]);
+            assert.equal(result.messages[0].message, results.error("could not find external image 'tiny-picture.png', path of input document is unknown").message);
         });
     });