Index: source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
===================================================================
--- source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
+++ source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
@@ -1252,10 +1252,10 @@
     return llvm::StringSwitch<uint32_t>(mode.str().c_str())
     .Case("r",   File::eOpenOptionRead)
     .Case("w",   File::eOpenOptionWrite)
-    .Case("a",   File::eOpenOptionAppend|File::eOpenOptionCanCreate)
+    .Case("a",   File::eOpenOptionWrite|File::eOpenOptionAppend|File::eOpenOptionCanCreate)
     .Case("r+",  File::eOpenOptionRead|File::eOpenOptionWrite)
     .Case("w+",  File::eOpenOptionRead|File::eOpenOptionWrite|File::eOpenOptionCanCreate|File::eOpenOptionTruncate)
-    .Case("a+",  File::eOpenOptionRead|File::eOpenOptionWrite|File::eOpenOptionCanCreate)
+    .Case("a+",  File::eOpenOptionRead|File::eOpenOptionWrite|File::eOpenOptionAppend|File::eOpenOptionCanCreate)
     .Default(0);
 }