diff --git a/etgtools/extractors.py b/etgtools/extractors.py
index c0a3eced..dc84fa62 100644
--- a/etgtools/extractors.py
+++ b/etgtools/extractors.py
@@ -291,7 +291,7 @@ class FunctionDef(BaseDef, FixWxPrefix):
         self.transferThis = False     # ownership of 'this' pointer transfered to C++
         self.cppCode = None           # Use this code instead of the default wrapper
         self.noArgParser = False      # set the NoargParser annotation
-        self.mustHaveAppFlag = False
+        self.preMethodCode = None
 
         self.__dict__.update(kw)
         if element is not None:
@@ -556,7 +556,11 @@ class FunctionDef(BaseDef, FixWxPrefix):
 
 
     def mustHaveApp(self, value=True):
-        self.mustHaveAppFlag = value
+        if value:
+            self.preMethodCode = "if (!wxPyCheckForApp()) return NULL;\n"
+        else:
+            self.preMethodCode = None
+
 
 #---------------------------------------------------------------------------
 
@@ -679,7 +683,7 @@ class ClassDef(BaseDef):
         self.innerclasses = []
         self.isInner = False        # Is this a nested class?
         self.klass = None           # if so, then this is the outer class
-        self.mustHaveAppFlag = False
+        self.preMethodCode = None
 
         # Stuff that needs to be generated after the class instead of within
         # it. Some back-end generators need to put stuff inside the class, and
@@ -1133,7 +1137,10 @@ private:
         self.addItem(wig)
 
     def mustHaveApp(self, value=True):
-        self.mustHaveAppFlag = value
+        if value:
+            self.preMethodCode = "if (!wxPyCheckForApp()) return NULL;\n"
+        else:
+            self.preMethodCode = None
 
 
     def copyFromClass(self, klass, name):
diff --git a/etgtools/sip_generator.py b/etgtools/sip_generator.py
index f8c7ed94..d3ff60fc 100644
--- a/etgtools/sip_generator.py
+++ b/etgtools/sip_generator.py
@@ -194,9 +194,9 @@ from .%s import *
                 # SIP appends them all together.
                 _needDocstring = False
 
-            if function.mustHaveAppFlag:
+            if function.preMethodCode:
                 stream.write('%PreMethodCode\n')
-                stream.write(nci("if (!wxPyCheckForApp()) return NULL;\n", 4))
+                stream.write(nci(function.preMethodCode, 4))
                 stream.write('%End\n')
 
             if function.cppCode:
@@ -426,11 +426,11 @@ from .%s import *
         if klass.ignored:
             return
 
-        # Propagate mustHaveApp setting to the ctors
-        if klass.mustHaveAppFlag:
+        # Propagate preMethodCode setting to the ctors
+        if klass.preMethodCode:
             for item in klass.allItems():
                 if isinstance(item, extractors.MethodDef) and item.isCtor:
-                    item.mustHaveApp(True)
+                    item.preMethodCode = klass.preMethodCode
 
         # write the class header
         if klass.templateParams:
@@ -680,9 +680,9 @@ from .%s import *
                 # SIP appends them all together.
                 _needDocstring = False
 
-            if method.mustHaveAppFlag:
+            if method.preMethodCode:
                 stream.write('%s%%PreMethodCode\n' % indent)
-                stream.write(nci("if (!wxPyCheckForApp()) return NULL;\n", len(indent)+4))
+                stream.write(nci(method.preMethodCode, len(indent)+4))
                 stream.write('%s%%End\n' % indent)
 
             if method.cppCode: