diff --git a/ChangeLog b/ChangeLog
index 64f4253128..1b03c6cd13 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2006-04-19  Andy Wingo  <wingo@pobox.com>
+
+	* gst/arg-types.py (GstCapsArg.write_const_param) 
+	(GstCapsArg.write_param): If there is a default value, initialize
+	the py_caps variable to NULL. PyArgs_Parse* doesn't touch c
+	variables if the optional arg isn't there. Fixes #339010.
+
 2006-04-19  Andy Wingo  <wingo@pobox.com>
 
 	* examples/remuxer.py (GstPlayer.seek): Don't do accurate seeks,
diff --git a/examples/fvumeter.py b/examples/fvumeter.py
index cabf09f593..a5380fda68 100644
--- a/examples/fvumeter.py
+++ b/examples/fvumeter.py
@@ -165,6 +165,7 @@ class FVUMeter(gtk.DrawingArea):
         self.style.set_background(self.window, gtk.STATE_NORMAL)
 
     def do_expose_event(self, event):
+        print 'foo'
         self.chain(event)
        
         x, y, w, h = self.allocation
@@ -235,5 +236,6 @@ class FVUMeter(gtk.DrawingArea):
             self.leftborder + vumeter_width + 5,
             self.topborder + int(vumeter_height / 2 - layout_height / 2),
             layout)
+        print 'bar'
 
 gobject.type_register(FVUMeter)
diff --git a/gst/arg-types.py b/gst/arg-types.py
index 6fa9efb5d3..a60aecfc4c 100644
--- a/gst/arg-types.py
+++ b/gst/arg-types.py
@@ -100,7 +100,11 @@ class GstCapsArg(ArgType):
             raise RuntimeError, "write_param not implemented for %s" % ptype
     
     def write_const_param(self, pname, pdflt, pnull, info):
-        info.varlist.add('PyObject', '*py_'+pname)
+        if pdflt:
+            assert pdflt == 'NULL'
+            info.varlist.add('PyObject', '*py_' + pname + ' = NULL')
+        else:
+            info.varlist.add('PyObject', '*py_' + pname)
         info.varlist.add('GstCaps', '*'+pname)
         info.varlist.add('gboolean', pname+'_is_copy')
 		info.add_parselist('O', ['&py_'+pname], [pname])
@@ -112,7 +116,11 @@ class GstCapsArg(ArgType):
         info.codeafter.append (self.after % { 'name' : pname, 'namecopy' : '&'+pname+'_is_copy' })
 	
     def write_normal_param(self, pname, pdflt, pnull, info):
-        info.varlist.add('PyObject', '*py_'+pname)
+        if pdflt:
+            assert pdflt == 'NULL'
+            info.varlist.add('PyObject', '*py_' + pname + ' = NULL')
+        else:
+            info.varlist.add('PyObject', '*py_' + pname)
         info.varlist.add('GstCaps', '*'+pname)
 		info.add_parselist('O', ['&py_'+pname], [pname])
         info.arglist.append(pname)