diff --git a/sipgen/gencode.c b/sipgen/gencode.c
--- a/sipgen/gencode.c
+++ b/sipgen/gencode.c
@@ -4574,7 +4574,7 @@
 {
     argType atype = vd->type.atype;
     const char *first_arg, *second_arg, *last_arg;
-    int needsNew, key;
+    int needsNew, var_key, self_key;
 
     if (generating_c || !isStaticVar(vd))
         first_arg = "sipSelf";
@@ -4584,9 +4584,33 @@
     last_arg = (generating_c || usedInCode(vd->getcode, "sipPyType")) ? "sipPyType" : "";
 
     needsNew = ((atype == class_type || atype == mapped_type) && vd->type.nrderefs == 0 && isConstArg(&vd->type));
-    key = ((atype == class_type || atype == mapped_type) && vd->type.nrderefs == 0) ? vd->module->next_key-- : 0;
-
-    second_arg = (generating_c || (key < 0 && !isStaticVar(vd))) ? "sipPySelf" : "";
+
+    /*
+     * If the variable is itself a non-const instance of a wrapped class then
+     * two things must happen.  Firstly, the getter must return the same Python
+     * object each time - it must not re-wrap the the instance.  This is
+     * because the Python object can contain important state information that
+     * must not be lost (specifically references to other Python objects that
+     * it owns).  Therefore the Python object wrapping the containing class
+     * must cache a reference to the Python object wrapping the variable.
+     * Secondly, the Python object wrapping the containing class must not be
+     * garbage collected before the Python object wrapping the variable is
+     * (because the latter references memory, ie. the variable itself, that is
+     * managed by the former).  Therefore the Python object wrapping the
+     * variable must keep a reference to the Python object wrapping the
+     * containing class (but only if the latter is non-static).
+     */
+    var_key = self_key = 0;
+
+    if (atype == class_type && vd->type.nrderefs == 0 && !isConstArg(&vd->type))
+    {
+        var_key = vd->type.u.cd->iff->module->next_key--;
+
+        if (!isStaticVar(vd))
+            self_key = vd->module->next_key--;
+    }
+
+    second_arg = (generating_c || var_key < 0 ) ? "sipPySelf" : "";
 
     prcode(fp,
 "\n"
@@ -4609,7 +4633,7 @@
 "    PyObject *sipPy;\n"
             );
     }
-    else if (key < 0)
+    else if (var_key < 0)
     {
         if (isStaticVar(vd))
             prcode(fp,
@@ -4662,10 +4686,10 @@
         return;
     }
 
-    if (key < 0)
+    /* Get any previously wrapped cached object. */
+    if (var_key < 0)
     {
         if (isStaticVar(vd))
-        {
             prcode(fp,
 "    if (sipPy)\n"
 "    {\n"
@@ -4674,16 +4698,14 @@
 "    }\n"
 "\n"
                 );
-        }
-        else
-        {
+        else
             prcode(fp,
 "    sipPy = sipGetReference(sipPySelf, %d);\n"
+"\n"
 "    if (sipPy)\n"
 "        return sipPy;\n"
 "\n"
-                , key);
-        }
+                , self_key);
     }
 
     if (needsNew)
@@ -4723,7 +4745,7 @@
                 iff = vd->type.u.cd->iff;
 
             prcode(fp,
-"    %s sipConvertFrom%sType(", (key < 0 ? "sipPy =" : "return"), (needsNew ? "New" : ""));
+"    %s sipConvertFrom%sType(", (var_key < 0 ? "sipPy =" : "return"), (needsNew ? "New" : ""));
 
             if (isConstArg(&vd->type))
                 prcode(fp, "const_cast<%b *>(sipVal)", &vd->type);
@@ -4733,18 +4755,26 @@
             prcode(fp, ", sipType_%C, NULL);\n"
                 , iff->fqcname);
 
-            if (key < 0)
-            {
+            if (var_key < 0)
+            {
+                prcode(fp,
+"\n"
+"    if (sipPy)\n"
+"    {\n"
+"        sipKeepReference(sipPy, %d, sipPySelf);\n"
+                    , var_key);
+
                 if (isStaticVar(vd))
                     prcode(fp,
-"    Py_XINCREF(sipPy);\n"
+"        Py_INCREF(sipPy);\n"
                         );
                 else
                     prcode(fp,
-"    sipKeepReference(sipPySelf, %d, sipPy);\n"
-                        , key);
-
-                prcode(fp,
+"        sipKeepReference(sipPySelf, %d, sipPy);\n"
+                        , self_key);
+
+                prcode(fp,
+"    }\n"
 "\n"
 "    return sipPy;\n"
                     );
@@ -4983,6 +5013,10 @@
     char *deref;
     int might_be_temp, keep, need_py, need_cpp;
 
+    /*
+     * We need to keep a reference to the original Python object if it
+     * providing the memory that the C/C++ variable is pointing to.
+     */
     keep = keepPyReference(&vd->type);
 
     if (generating_c || !isStaticVar(vd))
@@ -5149,12 +5183,10 @@
         }
         else
         {
-            vd->type.key = scope->module->next_key--;
-
             prcode(fp,
 "\n"
 "    sipKeepReference(sipPySelf, %d, sipPy);\n"
-                , vd->type.key);
+                , scope->module->next_key--);
         }
     }
 
diff --git a/siplib/sip.h.in.in b/siplib/sip.h.in.in
--- a/siplib/sip.h.in.in
+++ b/siplib/sip.h.in.in
@@ -1510,6 +1510,8 @@
             sipSimpleWrapper *, sip_gilstate_t);
     int (*api_init_mixin)(PyObject *self, PyObject *args, PyObject *kwds,
             const sipClassTypeDef *ctd);
+    PyObject *(*api_get_reference)(PyObject *self, int key);
+
     /*
      * The following are part of the public API.
      */
@@ -1530,10 +1532,6 @@
      */
     PyObject *(*api_invoke_slot_ex)(const sipSlot *slot, PyObject *sigargs,
             int check_receiver);
-    /*
-     * The following are not part of the public API.
-     */
-    PyObject *(*api_get_reference)(PyObject *self, int key);
 } sipAPIDef;
 
 
diff --git a/siplib/siplib.c.in b/siplib/siplib.c.in
--- a/siplib/siplib.c.in
+++ b/siplib/siplib.c.in
@@ -407,6 +407,7 @@
     sip_api_parse_result_ex,
     sip_api_call_error_handler,
     sip_api_init_mixin,
+    sip_api_get_reference,
     /*
      * The following are part of the public API.
      */
@@ -420,10 +421,6 @@
      * code.
      */
     sip_api_invoke_slot_ex,
-    /*
-     * The following are not part of the public API.
-     */
-    sip_api_get_reference,
 };
 
 
@@ -8534,6 +8531,7 @@
         return NULL;
 
     obj = PyDict_GetItem(dict, key_obj);
+    Py_DECREF(key_obj);
     Py_XINCREF(obj);
 
     return obj;