diff --git a/pinos/server/node.c b/pinos/server/node.c
index cdf83ad16..6cf3e5cee 100644
--- a/pinos/server/node.c
+++ b/pinos/server/node.c
@@ -175,6 +175,7 @@ pause_node (PinosNode *this)
     if ((res = spa_node_send_command (this->node, &cmd)) < 0)
       pinos_log_debug ("got error %d", res);
   }
+
   return res;
 }
 
@@ -208,6 +209,7 @@ suspend_node (PinosNode *this)
     if (p->allocated)
       pinos_memblock_free (&p->buffer_mem);
     p->allocated = false;
+    p->state = SPA_PORT_STATE_CONFIGURE;
   }
 
   spa_list_for_each (p, &this->output_ports, link) {
@@ -218,6 +220,7 @@ suspend_node (PinosNode *this)
     if (p->allocated)
       pinos_memblock_free (&p->buffer_mem);
     p->allocated = false;
+    p->state = SPA_PORT_STATE_CONFIGURE;
   }
   return res;
 }
@@ -735,6 +738,7 @@ pinos_node_get_free_port (PinosNode       *node,
   SpaList *ports;
   PinosPort *port = NULL, *p, **portmap;
   SpaPortIO *io;
+  SpaResult res;
   int i;
 
   if (direction == PINOS_DIRECTION_INPUT) {
@@ -769,8 +773,12 @@ pinos_node_get_free_port (PinosNode       *node,
           port = portmap[i] = pinos_port_new (node, direction, i);
           port->io = &io[i];
           (*n_ports)++;
-          spa_node_add_port (node->node, direction, i);
-          spa_node_port_set_io (node->node, direction, i, port->io);
+          if ((res = spa_node_add_port (node->node, direction, i)) < 0) {
+            pinos_log_error ("node %p: could not add port %d", node, i);
+          }
+          else {
+            spa_node_port_set_io (node->node, direction, i, port->io);
+          }
         }
       }
     } else {
diff --git a/spa/plugins/audiomixer/audiomixer.c b/spa/plugins/audiomixer/audiomixer.c
index a3c1270e5..ba77e6d38 100644
--- a/spa/plugins/audiomixer/audiomixer.c
+++ b/spa/plugins/audiomixer/audiomixer.c
@@ -576,6 +576,17 @@ spa_audiomixer_node_port_send_command (SpaNode        *node,
   return SPA_RESULT_NOT_IMPLEMENTED;
 }
 
+static void
+clear_buffer (SpaAudioMixer *this, MixerBuffer *out)
+{
+  int16_t *op;
+  size_t os;
+
+  op = SPA_MEMBER (out->outbuf->datas[0].data, out->outbuf->datas[0].chunk->offset, void);
+  os = out->outbuf->datas[0].chunk->size;
+  memset (op, 0, os);
+}
+
 static void
 add_port_data (SpaAudioMixer *this, MixerBuffer *out, SpaAudioMixerPort *port, int layer)
 {
@@ -634,7 +645,7 @@ spa_audiomixer_node_process_input (SpaNode *node)
     SpaAudioMixerPort *port = &this->in_ports[i];
     SpaPortIO *input;
 
-    if ((input = port->io) == NULL)
+    if ((input = port->io) == NULL || port->n_buffers == 0)
       continue;
 
     if (input->buffer_id != SPA_ID_INVALID) {
@@ -691,6 +702,9 @@ spa_audiomixer_node_process_input (SpaNode *node)
 
       add_port_data (this, outbuf, port, layer++);
     }
+    if (layer == 0)
+      clear_buffer (this, outbuf);
+
     output = outport->io;
     output->buffer_id = outbuf->outbuf->id;
     output->status = SPA_RESULT_OK;
diff --git a/spa/tests/test-mixer.c b/spa/tests/test-mixer.c
index bc911852a..3e0fdab18 100644
--- a/spa/tests/test-mixer.c
+++ b/spa/tests/test-mixer.c
@@ -403,13 +403,12 @@ negotiate_formats (AppData *data)
   if ((res = spa_node_add_port (data->mix, SPA_DIRECTION_INPUT, 0)) < 0)
     return res;
 
+  spa_node_port_set_io (data->source1, SPA_DIRECTION_OUTPUT, 0, &data->source1_mix_io[0]);
+  spa_node_port_set_io (data->mix, SPA_DIRECTION_INPUT, 0, &data->source1_mix_io[0]);
 
   if ((res = spa_node_port_set_format (data->mix, SPA_DIRECTION_INPUT, data->mix_ports[0], 0, format)) < 0)
     return res;
 
-  spa_node_port_set_io (data->source1, SPA_DIRECTION_OUTPUT, 0, &data->source1_mix_io[0]);
-  spa_node_port_set_io (data->mix, SPA_DIRECTION_INPUT, 0, &data->source1_mix_io[0]);
-
   if ((res = spa_node_port_set_format (data->source1, SPA_DIRECTION_OUTPUT, 0, 0, format)) < 0)
     return res;
 
@@ -424,12 +423,12 @@ negotiate_formats (AppData *data)
   if ((res = spa_node_add_port (data->mix, SPA_DIRECTION_INPUT, 1)) < 0)
     return res;
 
-  if ((res = spa_node_port_set_format (data->mix, SPA_DIRECTION_INPUT, data->mix_ports[1], 0, format)) < 0)
-    return res;
-
   spa_node_port_set_io (data->source2, SPA_DIRECTION_OUTPUT, 0, &data->source2_mix_io[0]);
   spa_node_port_set_io (data->mix, SPA_DIRECTION_INPUT, 1, &data->source2_mix_io[0]);
 
+  if ((res = spa_node_port_set_format (data->mix, SPA_DIRECTION_INPUT, data->mix_ports[1], 0, format)) < 0)
+    return res;
+
   if ((res = spa_node_port_set_format (data->source2, SPA_DIRECTION_OUTPUT, 0, 0, format)) < 0)
     return res;