diff --git a/packages/effection/src/resource.js b/packages/effection/src/resource.js
index 6390d6017..69c78d71d 100644
--- a/packages/effection/src/resource.js
+++ b/packages/effection/src/resource.js
@@ -5,7 +5,7 @@ let symbol = Symbol("resource");
 export function contextOf(resource) {
   if(resource instanceof ExecutionContext) {
     return resource;
-  } else if(typeof(resource) === "object" || typeof(resource) === "function") {
+  } else if(resource != null) {
     return resource[symbol];
   }
 }
diff --git a/packages/effection/tests/resources.test.js b/packages/effection/tests/resources.test.js
index 4f8470d33..1cbfc0ed1 100644
--- a/packages/effection/tests/resources.test.js
+++ b/packages/effection/tests/resources.test.js
@@ -107,4 +107,16 @@ describe('Returning resources', () => {
       });
     });
   });
+
+  describe('null operations', () => {
+    beforeEach(() => {
+      return execution = main(function*() {
+        yield Promise.resolve(null);
+      });
+    });
+    it('completes', () => {
+      expect(execution.state).toEqual('completed');
+    });
+  });
+
 });