diff --git a/externals/pdp/modules/generic/pdp_metro.c b/externals/pdp/modules/generic/pdp_metro.c
index ebcc84e4e1718763f05c7accdfc9f2bff66b2e8e..9e3e96b575751a41af5361f3238b86ede882c21c 100644
--- a/externals/pdp/modules/generic/pdp_metro.c
+++ b/externals/pdp/modules/generic/pdp_metro.c
@@ -125,7 +125,7 @@ void pdp_metro_setup(void)
 
     CLASS_MAINSIGNALIN(metro_class, t_metro, x_f);   
     class_addmethod(metro_class, (t_method)metro_tick,   gensym("tick"),  A_NULL);
-    class_addmethod(metro_class, (t_method)metro_dsp,    gensym("dsp"),  A_NULL);
+    class_addmethod(metro_class, (t_method)metro_dsp,    gensym("dsp"),  A_CANT, A_NULL);
     class_addmethod(metro_class, (t_method)metro_fps,    gensym("fps"),  A_FLOAT, A_DEFFLOAT, A_NULL);
 
 
diff --git a/externals/pdp/modules/generic/pdp_rawout.c b/externals/pdp/modules/generic/pdp_rawout.c
index 1163a28ceb501dcfc3fc4ac879ad66bc94ceda7d..dc7514a63ca001139508d42128583a9869956ed6 100644
--- a/externals/pdp/modules/generic/pdp_rawout.c
+++ b/externals/pdp/modules/generic/pdp_rawout.c
@@ -522,7 +522,7 @@ void pdp_rawout_setup(void){
 
     /* add signal input */
     CLASS_MAINSIGNALIN(rawout_dsp_class, t_rawout, x_f); 
-    class_addmethod(rawout_dsp_class, (t_method)rawout_dsp, gensym("dsp"), 0);   
+    class_addmethod(rawout_dsp_class, (t_method)rawout_dsp, gensym("dsp"), A_CANT, 0);   
     COMMON(rawout_dsp_class);
 
 }
diff --git a/externals/pdp/modules/image_io/pdp_qt.c b/externals/pdp/modules/image_io/pdp_qt.c
index 58023033d53c8e18445ee7aaca6155a905a3f885..f5fdd65e81b9198d3b54914d5550b3e69b2a6d8e 100644
--- a/externals/pdp/modules/image_io/pdp_qt.c
+++ b/externals/pdp/modules/image_io/pdp_qt.c
@@ -971,7 +971,7 @@ void pdp_qt_setup(void)
     	(t_method)pdp_qt_free, sizeof(t_pdp_qt), 0, A_NULL);
     pdp_qt_setup_common(pdp_qt_tilde_class);
 
-    class_addmethod(pdp_qt_tilde_class, (t_method)pdp_qt_dsp, gensym("dsp"), 0);
+    class_addmethod(pdp_qt_tilde_class, (t_method)pdp_qt_dsp, gensym("dsp"), A_CANT, 0);
 
 #ifdef __APPLE__
     /* this is necessary for pdp_qt to find the embedded libquicktime plugins */
diff --git a/externals/pdp/modules/image_special/pdp_scan.c b/externals/pdp/modules/image_special/pdp_scan.c
index 482a9661906491f210c29f118c5f90a8f187e7fe..2efdd0457a21488cefa21c3009edcecc5e63f432 100644
--- a/externals/pdp/modules/image_special/pdp_scan.c
+++ b/externals/pdp/modules/image_special/pdp_scan.c
@@ -221,7 +221,7 @@ void pdp_scan_setup(void)
 
     class_addmethod(pdp_scan_class, (t_method)pdp_scan_interpolate, gensym("interpolate"), A_FLOAT, A_NULL);
     class_addmethod(pdp_scan_class, (t_method)pdp_scan_input_0, gensym("pdp"),  A_SYMBOL, A_DEFFLOAT, A_NULL);
-    class_addmethod(pdp_scan_class, (t_method)pdp_scan_dsp, gensym("dsp"),  A_NULL);
+    class_addmethod(pdp_scan_class, (t_method)pdp_scan_dsp, gensym("dsp"), A_CANT, A_NULL);
 
 
 }
diff --git a/externals/pdp/modules/image_special/pdp_scanxy.c b/externals/pdp/modules/image_special/pdp_scanxy.c
index fe6efb979e01b86ff483843e1867245298a8fbe1..90d96e5acce8bc9ce583f54be6901c378530acc0 100644
--- a/externals/pdp/modules/image_special/pdp_scanxy.c
+++ b/externals/pdp/modules/image_special/pdp_scanxy.c
@@ -197,7 +197,7 @@ void pdp_scanxy_setup(void)
 
     class_addmethod(pdp_scanxy_class, (t_method)pdp_scanxy_interpolate, gensym("interpolate"), A_FLOAT, A_NULL);
     class_addmethod(pdp_scanxy_class, (t_method)pdp_scanxy_input_0, gensym("pdp"),  A_SYMBOL, A_DEFFLOAT, A_NULL);
-    class_addmethod(pdp_scanxy_class, (t_method)pdp_scanxy_dsp, gensym("dsp"),  A_NULL);
+    class_addmethod(pdp_scanxy_class, (t_method)pdp_scanxy_dsp, gensym("dsp"), A_CANT, A_NULL);
 
 
 }
diff --git a/externals/pdp/modules/image_special/pdp_scope.c b/externals/pdp/modules/image_special/pdp_scope.c
index a1d28ccdebc6ad9f4f26ff4e816732bd66b05423..5b28b85b768a9634a99763ecdb0eb1d2db364a71 100644
--- a/externals/pdp/modules/image_special/pdp_scope.c
+++ b/externals/pdp/modules/image_special/pdp_scope.c
@@ -309,7 +309,7 @@ void pdp_scope_setup(void)
     class_addmethod(pdp_scope_class, (t_method)pdp_scope_type, gensym("type"), A_SYMBOL, A_NULL);
     class_addmethod(pdp_scope_class, (t_method)pdp_scope_dim, gensym("dim"), A_FLOAT, A_FLOAT, A_NULL);
     class_addmethod(pdp_scope_class, (t_method)pdp_scope_bang, gensym("bang"), A_NULL);
-    class_addmethod(pdp_scope_class, (t_method)pdp_scope_dsp, gensym("dsp"), 0); 
+    class_addmethod(pdp_scope_class, (t_method)pdp_scope_dsp, gensym("dsp"), A_CANT, 0); 
 }
 
 #ifdef __cplusplus