2 files changed, 9 insertions, 4 deletions

diff --git a/bitbake/lib/bb/data_smart.py b/bitbake/lib/bb/data_smart.py
index 43e9e78555..65528c6ae6 100644
--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -750,8 +750,6 @@ class DataSmart(MutableMapping):
 
 
         if flag == "_content" and local_var is not None and ":append" in local_var and not parsing:
-            if not value:
-                value = ""
             self.need_overrides()
             for (r, o) in local_var[":append"]:
                 match = True
@@ -760,11 +758,11 @@ class DataSmart(MutableMapping):
                         if not o2 in self.overrides:
                             match = False                            
                 if match:
+                    if value is None:
+                        value = ""
                     value = value + r
 
         if flag == "_content" and local_var is not None and ":prepend" in local_var and not parsing:
-            if not value:
-                value = ""
             self.need_overrides()
             for (r, o) in local_var[":prepend"]:
 
@@ -774,6 +772,8 @@ class DataSmart(MutableMapping):
                         if not o2 in self.overrides:
                             match = False                            
                 if match:
+                    if value is None:
+                        value = ""
                     value = r + value
 
         parser = None
diff --git a/bitbake/lib/bb/tests/data.py b/bitbake/lib/bb/tests/data.py
index 7f1d3ffbbc..e667c7c7d3 100644
--- a/bitbake/lib/bb/tests/data.py
+++ b/bitbake/lib/bb/tests/data.py
@@ -405,6 +405,11 @@ class TestOverrides(unittest.TestCase):
         bb.data.expandKeys(self.d)
         self.assertEqual(self.d.getVar("VERSION"), "2")
 
+    def test_append_and_unused_override(self):
+        # Had a bug where an unused override append could return "" instead of None
+        self.d.setVar("BAR:append:unusedoverride", "testvalue2")
+        self.assertEqual(self.d.getVar("BAR"), None)
+
 class TestKeyExpansion(unittest.TestCase):
     def setUp(self):
         self.d = bb.data.init()