diff --git a/m-funcobj.h b/m-funcobj.h
index 53c6fad4..53dc4285 100644
--- a/m-funcobj.h
+++ b/m-funcobj.h
@@ -38,6 +38,17 @@
   M_END_PROTECTED_CODE
 
 
+/* Define a function object interface of name 'name'
+ * as the given name name_t
+ * USAGE:
+ *    FUNC_OBJ_ITF_DEF_AS(name, name_t, retcode type, type of param1, type of param 2, ...)
+ */
+#define FUNC_OBJ_ITF_DEF_AS(name, name_t, ...)                          \
+  M_BEGIN_PROTECTED_CODE                                                \
+  M_IF_NARGS_EQ1(__VA_ARGS__)(FUNCOBJI_ITF_NO_PARAM_DEF, FUNCOBJI_ITF_PARAM_DEF)(name, name_t, __VA_ARGS__) \
+  M_END_PROTECTED_CODE
+
+
 /* Define a function object instance of name 'name' based on the interface 'base_name'
  * The function is defined as per :
  * - the prototype of the inherited interface
@@ -62,6 +73,19 @@
   M_END_PROTECTED_CODE
 
 
+/* Define a function object instance of name 'name' based on the interface 'base_name'
+ * as the given name name_t.
+ * See FUNC_OBJ_INS_DEF for additional details.
+ * 
+ * USAGE/EXAMPLE:
+ *   FUNC_OBJ_INS_DEF_AS(name, name_t, base_name, (param1, ...), { return param1 * self->member1 }, (member1, int), ...)
+ */
+#define FUNC_OBJ_INS_DEF_AS(name, name_t, base_name, param_list, ...)   \
+  M_BEGIN_PROTECTED_CODE                                                \
+  M_IF_NARGS_EQ1(__VA_ARGS__)(FUNCOBJI_INS_NO_ATTR_DEF, FUNCOBJI_INS_ATTR_DEF)(name, name_t, base_name, param_list, __VA_ARGS__) \
+  M_END_PROTECTED_CODE
+
+
 /* OPLIST of the instanced function object
  * USAGE:
  *  FUNC_OBJ_INS_OPLIST(name, oplist of the attr1, ...)
@@ -282,7 +306,7 @@
   FUNCOBJI_CONTROL_ALL_OPLIST(name, __VA_ARGS__)                        \
                                                                         \
   static inline M_C(base_name, _retcode_ct)                             \
-  M_C(name, _callback)(M_C(base_name, _t) _self                         \
+  M_C(name, _callback)(M_C(base_name, _ct) _self                        \
                       M_IF_EMPTY(M_OPFLAT param_list)(                  \
                         /* No param */,                                 \
                         M_MAP3(FUNCOBJI_INS_ARGLIST, base_name, M_OPFLAT param_list)\
diff --git a/tests/test-mfuncobj.c b/tests/test-mfuncobj.c
index a5b37e4d..db542820 100644
--- a/tests/test-mfuncobj.c
+++ b/tests/test-mfuncobj.c
@@ -69,6 +69,17 @@ END_COVERAGE
 
 #define M_OPL_instance22_t() FUNC_OBJ_INS_OPLIST(instance22, M_DEFAULT_OPLIST)
 
+FUNC_OBJ_ITF_DEF_AS(Interface, Interface, double, double)
+
+FUNC_OBJ_INS_DEF_AS(Instance, Instance,
+                    Interface,
+                    (a), {
+                      return a * self->a + self->b;
+                    },
+                    (a, double),
+                    (b, double) )
+#define M_OPL_Instance() FUNC_OBJ_INS_OPLIST(Instance, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST)
+
 static void test_instance11(void)
 {
   instance11_t cmp;
@@ -117,11 +128,20 @@ static void test_instance22(void)
   }
 }
 
+static void test_double(void)
+{
+  M_LET( (func, 2.0, 3.0), Instance) {
+    double d = Interface_call(Instance_as_interface(func), 4.0);
+    assert (d == 2.0 * 4.0 + 3.0);
+  }
+}
+
 int main(void)
 {
   test_instance11();
   test_instance12();
   test_instance21();
   test_instance22();
+  test_double();
   return 0;
 }