2 files changed, 11 insertions, 1 deletions
diff --git a/src/engine/SCons/Action.py b/src/engine/SCons/Action.py
index c95644a..c8d62cd 100644
--- a/src/engine/SCons/Action.py
+++ b/src/engine/SCons/Action.py
@@ -412,7 +412,10 @@ class CommandGeneratorAction(ActionBase):
             source = [source]
         rsources = map(rfile, source)
         act = self.__generate(target, source, env, 0)
-        return act.strfunction(target, rsources, env)
+        if act.strfunction:
+            return act.strfunction(target, rsources, env)
+        else:
+            return None
 
     def __str__(self):
         try:
diff --git a/src/engine/SCons/ActionTests.py b/src/engine/SCons/ActionTests.py
index b3d7e8c..f699e61 100644
--- a/src/engine/SCons/ActionTests.py
+++ b/src/engine/SCons/ActionTests.py
@@ -1006,6 +1006,13 @@ class CommandGeneratorActionTestCase(unittest.TestCase):
         s = a.strfunction([], [], env=Environment())
         assert s == "sf was called", s
 
+        def f(target, source, env, for_signature, self=self):
+            def null(target, source, env):
+                pass
+            return SCons.Action.Action(null, strfunction=None)
+        a = SCons.Action.CommandGeneratorAction(f)
+        s = a.strfunction([], [], env=Environment())
+
     def test_execute(self):
         """Test executing a command generator Action
         """