diff --git a/ChangeLog b/ChangeLog
index ce9d9920c2..d6239e43ee 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2008-10-03  Wim Taymans  <wim.taymans@collabora.co.uk>
+
+	* sys/v4l2/gstv4l2object.h:
+	Getting the Class from an instance is not just a matter of casting it to
+	the class struct but it involves calling G_OBJECT_GET_CLASS on the
+	instance. Fixes #549784.
+
 2008-10-01  Michael Smith <msmith@songbirdnest.com>
 
 	* configure.ac:
diff --git a/sys/v4l2/gstv4l2object.h b/sys/v4l2/gstv4l2object.h
index 0c5cdbcbe6..5eb557ed67 100644
--- a/sys/v4l2/gstv4l2object.h
+++ b/sys/v4l2/gstv4l2object.h
@@ -157,7 +157,7 @@ interface_as_function ## _probe_probe_property (GstPropertyProbe * probe,
 			                        guint prop_id,                              \
                                                 const GParamSpec * pspec)                   \
 {                                                                                           \
-  Type_Class *this_class = (Type_Class*) probe;                                             \
+  Type_Class *this_class = (Type_Class*) G_OBJECT_GET_CLASS (probe);                        \
   gst_v4l2_probe_probe_property (probe, prop_id, pspec,                                     \
                                         &this_class->v4l2_class_devices);	            \
 }                                                                                           \
@@ -167,7 +167,7 @@ interface_as_function ## _probe_needs_probe (GstPropertyProbe * probe,
 			                     guint prop_id,                                 \
                                              const GParamSpec * pspec)                      \
 {                                                                                           \
-  Type_Class *this_class = (Type_Class*) probe;                                             \
+  Type_Class *this_class = (Type_Class*) G_OBJECT_GET_CLASS (probe);                        \
   return gst_v4l2_probe_needs_probe (probe, prop_id, pspec,                                 \
                                         &this_class->v4l2_class_devices);	            \
 }                                                                                           \
@@ -177,7 +177,7 @@ interface_as_function ## _probe_get_values (GstPropertyProbe * probe,
 			                    guint prop_id,                                  \
                                             const GParamSpec * pspec)                       \
 {                                                                                           \
-  Type_Class *this_class = (Type_Class*) probe;                                             \
+  Type_Class *this_class = (Type_Class*) G_OBJECT_GET_CLASS (probe);                        \
   return gst_v4l2_probe_get_values (probe, prop_id, pspec,                                  \
                                     &this_class->v4l2_class_devices);	                    \
 }                                                                                           \