diff --git a/commcare_export/env.py b/commcare_export/env.py
index b885a696..df2567a4 100644
--- a/commcare_export/env.py
+++ b/commcare_export/env.py
@@ -346,7 +346,10 @@ def count_selected(val):
 
 def join(*args):
     args = [unwrap_val(arg)for arg in args]
-    return args[0].join(args[1:])
+    try:
+        return args[0].join(args[1:])
+    except TypeError:
+        return '""'
 
 
 @unwrap('val')
diff --git a/tests/test_excel_query.py b/tests/test_excel_query.py
index 3176ef89..60104859 100644
--- a/tests/test_excel_query.py
+++ b/tests/test_excel_query.py
@@ -208,6 +208,9 @@ def test_compile_mapped_field(self):
         expression = compile_mapped_field({'a': 'mapped from a'}, Reference('foo.baz'))
         assert list(expression.eval(env))[0].value == 'b'
 
+        expression = compile_mapped_field({'a': 'mapped from a'}, Reference('foo.boo'))
+        assert list(expression.eval(env)) == []
+
     def test_get_queries_from_excel(self):
         minilinq = Bind('checkpoint_manager', Apply(Reference('get_checkpoint_manager'), Literal(["Forms"])),
             Emit(