diff --git a/oletools/oleid.py b/oletools/oleid.py
index 8542f4b..f6b050b 100644
--- a/oletools/oleid.py
+++ b/oletools/oleid.py
@@ -54,6 +54,7 @@ from __future__ import print_function
 # 2016-10-25 v0.50 PL: - fixed print and bytes strings for Python 3
 # 2016-12-12 v0.51 PL: - fixed relative imports for Python 3 (issue #115)
 # 2017-04-26       PL: - fixed absolute imports (issue #141)
+# 2017-09-01       SA: - detect OpenXML encryption
 
 __version__ = '0.51'
 
@@ -211,6 +212,9 @@ class OleID:
         if 0x13 in self.suminfo:
             if self.suminfo[0x13] & 1:
                 self.encrypted.value = True
+        # check if this is an OpenXML encrypted file
+        elif self.ole.exists('EncryptionInfo'):
+            self.encrypted.value = True
 
     def check_word (self):
         word = Indicator('word', False, name='Word Document',
diff --git a/tests/oleid/__init__.py b/tests/oleid/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tests/oleid/__init__.py
diff --git a/tests/oleid/test_issue_166.py b/tests/oleid/test_issue_166.py
new file mode 100644
index 0000000..c350c00
--- /dev/null
+++ b/tests/oleid/test_issue_166.py
@@ -0,0 +1,26 @@
+"""
+Test if oleid detects encrypted documents
+"""
+
+import unittest, sys, os
+
+from tests.test_utils import DATA_BASE_DIR
+from os.path import join
+
+from oletools import oleid
+
+class TestEncryptedDocumentDetection(unittest.TestCase):
+    def test_encrypted_document_detection(self):
+        """ Run oleid and check if the document is flagged as encrypted """
+        filename = join(DATA_BASE_DIR, 'basic/encrypted.docx')
+
+        oleid_instance = oleid.OleID(filename)
+        indicators = oleid_instance.check()
+
+        is_encrypted = next(i.value for i in indicators if i.id == 'encrypted')
+
+        self.assertEqual(is_encrypted, True)
+
+# just in case somebody calls this file as a script
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file
diff --git a/tests/test-data/basic/encrypted.docx b/tests/test-data/basic/encrypted.docx
new file mode 100644
index 0000000..0f7a916
--- /dev/null
+++ b/tests/test-data/basic/encrypted.docx