diff --git a/channels/audin/server/audin.c b/channels/audin/server/audin.c
index 44d66dbec..f5216676d 100644
--- a/channels/audin/server/audin.c
+++ b/channels/audin/server/audin.c
@@ -70,7 +70,7 @@ typedef struct _audin_server
  * @return 0 on success, otherwise a Win32 error code
  */
 static UINT audin_server_select_format(audin_server_context* context,
-                                       int client_format_index)
+                                       size_t client_format_index)
 {
 	audin_server* audin = (audin_server*) context;
 
@@ -81,7 +81,7 @@ static UINT audin_server_select_format(audin_server_context* context,
 		return ERROR_INVALID_DATA;
 	}
 
-	context->selected_client_format = client_format_index;
+	context->selected_client_format = (SSIZE_T)client_format_index;
 
 	if (!freerdp_dsp_context_reset(audin->dsp_context,
 	                               &audin->context.client_formats[client_format_index]))
diff --git a/include/freerdp/server/audin.h b/include/freerdp/server/audin.h
index ac49551f9..ade14abfd 100644
--- a/include/freerdp/server/audin.h
+++ b/include/freerdp/server/audin.h
@@ -28,7 +28,7 @@
 
 typedef struct _audin_server_context audin_server_context;
 
-typedef UINT(*psAudinServerSelectFormat)(audin_server_context* context, int client_format_index);
+typedef UINT(*psAudinServerSelectFormat)(audin_server_context* context, size_t client_format_index);
 typedef BOOL (*psAudinServerOpen)(audin_server_context* context);
 typedef BOOL (*psAudinServerIsOpen)(audin_server_context* context);
 typedef BOOL (*psAudinServerClose)(audin_server_context* context);
diff --git a/server/shadow/shadow_audin.c b/server/shadow/shadow_audin.c
index 85a38afe7..7d0f144ea 100644
--- a/server/shadow/shadow_audin.c
+++ b/server/shadow/shadow_audin.c
@@ -60,8 +60,7 @@ static UINT AudinServerOpening(audin_server_context* context)
 		return CHANNEL_RC_OK;
 	}
 
-	context->SelectFormat(context, i);
-	return CHANNEL_RC_OK;
+	return IFCALLRESULT(ERROR_CALL_NOT_IMPLEMENTED, context->SelectFormat, context, i);
 }
 /**
  * Function description