diff --git a/indra/assemblers/graph/assembler.py b/indra/assemblers/graph/assembler.py
index <HASH>..<HASH> 100644
--- a/indra/assemblers/graph/assembler.py
+++ b/indra/assemblers/graph/assembler.py
@@ -142,6 +142,7 @@ class GraphAssembler():
                 self._add_complex(stmt.members)
             elif all([ag is not None for ag in stmt.agent_list()]):
                 self._add_stmt_edge(stmt)
+        return self.get_string()
 
     def get_string(self):
         """Return the assembled graph as a string.
diff --git a/indra/tests/test_graph_assembler.py b/indra/tests/test_graph_assembler.py
index <HASH>..<HASH> 100644
--- a/indra/tests/test_graph_assembler.py
+++ b/indra/tests/test_graph_assembler.py
@@ -8,7 +8,8 @@ def test_phosphorylation():
     st = [Phosphorylation(Agent('MAP2K1'), Agent('MAPK1'))]
     ga = GraphAssembler()
     ga.add_statements(st)
-    ga.make_model()
+    model = ga.make_model()
+    assert 'MAP2K1' in model
     assert len(ga.graph.nodes()) == 2
     assert len(ga.graph.edges()) == 1
Return agraph string when assembling graph