diff --git a/pyxform/constants.py b/pyxform/constants.py
index bb5fb0510..dea5fa00c 100644
--- a/pyxform/constants.py
+++ b/pyxform/constants.py
@@ -69,4 +69,14 @@
 OSM = u"osm"
 OSM_TYPE = u"binary"
 
-NAMESPACES = u'namespaces'
+NAMESPACES = u"namespaces"
+
+SUPPORTED_SHEET_NAMES = [
+    SURVEY,
+    CASCADING_CHOICES,
+    CHOICES,
+    COLUMNS,
+    CHOICES_AND_COLUMNS,
+    SETTINGS,
+    OSM,
+]
diff --git a/pyxform/tests/bug_example_xls/xl_date_ambiguous.xlsx b/pyxform/tests/bug_example_xls/xl_date_ambiguous.xlsx
new file mode 100644
index 000000000..a179258fe
Binary files /dev/null and b/pyxform/tests/bug_example_xls/xl_date_ambiguous.xlsx differ
diff --git a/pyxform/tests/bug_tests.py b/pyxform/tests/bug_tests.py
index e67b7dc71..49a7fd93b 100644
--- a/pyxform/tests/bug_tests.py
+++ b/pyxform/tests/bug_tests.py
@@ -219,5 +219,16 @@ def test_blank_second_row(self):
         self.assertTrue(len(survey_dict) > 0)
 
 
-if __name__ == '__main__':
+class TestXLDateAmbigous(unittest.TestCase):
+    """Test non standard sheet with exception is processed successfully."""
+    def test_xl_date_ambigous(self):
+        """Test non standard sheet with exception is processed successfully."""
+        filename = "xl_date_ambiguous.xlsx"
+        path_to_excel_file = os.path.join(DIR, "bug_example_xls", filename)
+        xls_reader = SurveyReader(path_to_excel_file)
+        survey_dict = xls_reader.to_json_dict()
+        self.assertTrue(len(survey_dict) > 0)
+
+
+if __name__ == "__main__":
     unittest.main()
diff --git a/pyxform/xls2json_backends.py b/pyxform/xls2json_backends.py
index a805b066b..d139459fc 100644
--- a/pyxform/xls2json_backends.py
+++ b/pyxform/xls2json_backends.py
@@ -210,11 +210,16 @@ def slugify(s):
 
     result = OrderedDict()
     for sheet in workbook.sheets():
+        # Do not process sheets that have nothing to do with XLSForm.
+        if sheet.name not in constants.SUPPORTED_SHEET_NAMES:
+            continue
         if sheet.name == constants.CASCADING_CHOICES:
             result[sheet.name] = _xls_to_dict_cascade_sheet(sheet)
         else:
-            result[sheet.name], result[u"%s_header" % sheet.name] = \
-                xls_to_dict_normal_sheet(sheet)
+            result[sheet.name], result[
+                u"%s_header" % sheet.name
+            ] = xls_to_dict_normal_sheet(sheet)
+
     return result