diff --git a/include/App/appclient.h b/include/App/appclient.h
index a6be0ba..ea3c19b 100644
--- a/include/App/appclient.h
+++ b/include/App/appclient.h
@@ -35,7 +35,9 @@ AppClient * appclient_new_event(char const * app, char const * name,
 void appclient_delete(AppClient * appclient);
 
 /* useful */
-int appclient_call(AppClient * appclient, Variable ** ret,
-		char const * method, ...);
+int appclient_call(AppClient * appclient,
+		void ** result, char const * method, ...);
+int appclient_call_variable(AppClient * appclient,
+		Variable * result, char const * method, ...);
 
 #endif /* !LIBAPP_APP_APPCLIENT_H */
diff --git a/src/appclient.c b/src/appclient.c
index b9a9df4..ed58989 100644
--- a/src/appclient.c
+++ b/src/appclient.c
@@ -115,7 +115,21 @@ char const * appclient_get_app(AppClient * appclient)
 /* useful */
 /* appclient_call */
 int appclient_call(AppClient * appclient,
-		void ** result, char const * function, ...)
+		void ** result, char const * method, ...)
+{
+	int ret;
+	va_list ap;
+
+	va_start(ap, method);
+	ret = appinterface_callv(appclient->interface, result, method, ap);
+	va_end(ap);
+	return ret;
+}
+
+
+/* appclient_call_variable */
+int appclient_call_variable(AppClient * appclient,
+		Variable * result, char const * method, ...)
 {
 	int ret;
 	size_t cnt;
@@ -123,17 +137,16 @@ int appclient_call(AppClient * appclient,
 	va_list ap;
 	Variable ** argv;
 
-	if(appinterface_get_args_count(appclient->interface, &cnt, function)
-			!= 0)
+	if(appinterface_get_args_count(appclient->interface, &cnt, method) != 0)
 		return -1;
 	if((argv = malloc(sizeof(*argv) * cnt)) == NULL)
 		return error_set_code(-errno, "%s", strerror(errno));
-	va_start(ap, function);
+	va_start(ap, method);
 	for(i = 0; i < cnt; i++)
 		argv[i] = va_arg(ap, Variable *);
 	va_end(ap);
-	ret = appinterface_callv(appclient->interface, result, function, cnt,
-			argv);
+	ret = appinterface_call_variablev(appclient->interface, result, method,
+			cnt, argv);
 	free(argv);
 	return ret;
 }
diff --git a/src/appinterface.c b/src/appinterface.c
index 4552988..307444e 100644
--- a/src/appinterface.c
+++ b/src/appinterface.c
@@ -388,18 +388,21 @@ int appinterface_get_args_count(AppInterface * appinterface, size_t * count,
 /* useful */
 /* appinterface_callv */
 int appinterface_callv(AppInterface * appinterface, void ** result,
-		char const * method, size_t argc, Variable ** argv)
+		char const * method, va_list args)
 {
 	int ret;
 	AppInterfaceCall * call;
-	Variable * r = NULL;
+	Variable * r;
 
 	if((call = _appinterface_get_call(appinterface, method)) == NULL)
 		return -1;
-	if(argc != call->args_cnt)
+	/* FIXME implement argv */
+	if(call->type.type == VT_NULL)
+		r = NULL;
+	else if((r = variable_new(call->type.type, NULL)) == NULL)
 		return -1;
-	if((ret = marshall_call(call->type.type, &r, call->func, argc, argv))
-			== 0 && r != NULL)
+	if((ret = marshall_call(call->type.type, r, call->func, call->args_cnt,
+					NULL)) == 0 && r != NULL)
 	{
 		if(result != NULL)
 			/* XXX return 0 anyway? */
@@ -410,6 +413,21 @@ int appinterface_callv(AppInterface * appinterface, void ** result,
 }
 
 
+/* appinterface_call_variablev */
+int appinterface_call_variablev(AppInterface * appinterface, Variable * result,
+		char const * method, size_t argc, Variable ** argv)
+{
+	AppInterfaceCall * call;
+
+	if((call = _appinterface_get_call(appinterface, method)) == NULL)
+		return -1;
+	if(argc != call->args_cnt)
+		return -1;
+	/* FIXME implement argv */
+	return marshall_call(call->type.type, result, call->func, argc, NULL);
+}
+
+
 /* private */
 /* appinterface_get_call */
 static AppInterfaceCall * _appinterface_get_call(AppInterface * appinterface,
diff --git a/src/appinterface.h b/src/appinterface.h
index 22516e8..74cca41 100644
--- a/src/appinterface.h
+++ b/src/appinterface.h
@@ -42,6 +42,8 @@ int appinterface_get_args_count(AppInterface * appinterface, size_t * count,
 
 /* useful */
 int appinterface_callv(AppInterface * appinterface, void ** result,
+		char const * method, va_list args);
+int appinterface_call_variablev(AppInterface * appinterface, Variable * result,
 		char const * method, size_t argc, Variable ** argv);
 
 #endif /* !LIBAPP_APPINTERFACE_H */
diff --git a/src/appserver.c b/src/appserver.c
index c945b8f..95ebdbd 100644
--- a/src/appserver.c
+++ b/src/appserver.c
@@ -158,8 +158,8 @@ static int _helper_message_call(AppServer * appserver, AppTransport * transport,
 	if(!appinterface_can_call(appserver->interface, name, method))
 		/* XXX report errors */
 		return -1;
-	ret = appinterface_callv(appserver->interface, &result, method, 0,
-			NULL);
+	ret = appinterface_call_variablev(appserver->interface, result, method,
+			0, NULL);
 	if(result != NULL)
 		variable_delete(result);
 	return ret;
diff --git a/src/marshall.c b/src/marshall.c
index 730a635..e0c49ef 100644
--- a/src/marshall.c
+++ b/src/marshall.c
@@ -15,16 +15,18 @@
 
 
 
-#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+#include <System/error.h>
 #include "marshall.h"
 
 
 /* Marshall */
 /* public */
 /* functions */
-static int _call0(VariableType type, Variable ** result, void * func);
+static int _call0(VariableType type, Variable * result, void * func);
 
-int marshall_call(VariableType type, Variable ** result, void * func,
+int marshall_call(VariableType type, Variable * result, void * func,
 		size_t argc, Variable ** argv)
 {
 	if(argc == 0)
@@ -33,9 +35,9 @@ int marshall_call(VariableType type, Variable ** result, void * func,
 	return -1;
 }
 
-static int _call0(VariableType type, Variable ** result, void * func)
+static int _call0(VariableType type, Variable * result, void * func)
 {
-	Variable * v;
+	int ret = 0;
 	union
 	{
 		void * call;
@@ -54,7 +56,7 @@ static int _call0(VariableType type, Variable ** result, void * func)
 	} f;
 	union
 	{
-		uint8_t bool;
+		uint8_t b;
 		int8_t i8;
 		uint8_t u8;
 		int16_t i16;
@@ -69,61 +71,68 @@ static int _call0(VariableType type, Variable ** result, void * func)
 
 	/* FIXME implement through the generic marshaller instead */
 	f.call = func;
-	if((v = variable_new(type, NULL)) == NULL)
-		return -1;
 	switch(type)
 	{
 		case VT_NULL:
 			f.call_null();
 			break;
 		case VT_BOOL:
-			res.bool = (f.call_bool() != 0) ? 1 : 0;
-			variable_set_from(v, type, &res.bool);
+			res.b = (f.call_bool() != 0) ? 1 : 0;
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.b);
 			break;
 		case VT_INT8:
 			res.i8 = f.call_i8();
-			variable_set_from(v, type, &res.i8);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.i8);
 			break;
 		case VT_UINT8:
 			res.u8 = f.call_u8();
-			variable_set_from(v, type, &res.u8);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.u8);
 			break;
 		case VT_INT16:
 			res.i16 = f.call_i16();
-			variable_set_from(v, type, &res.i16);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.i16);
 			break;
 		case VT_UINT16:
 			res.u16 = f.call_u16();
-			variable_set_from(v, type, &res.u16);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.u16);
 			break;
 		case VT_INT32:
 			res.i32 = f.call_i32();
-			variable_set_from(v, type, &res.i32);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.i32);
 			break;
 		case VT_UINT32:
 			res.u32 = f.call_u32();
-			variable_set_from(v, type, &res.u32);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.u32);
 			break;
 		case VT_INT64:
 			res.i64 = f.call_i64();
-			variable_set_from(v, type, &res.i64);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.i64);
 			break;
 		case VT_UINT64:
 			res.u64 = f.call_u64();
-			variable_set_from(v, type, &res.u64);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.u64);
 			break;
 		case VT_FLOAT:
 			res.f = f.call_f();
-			variable_set_from(v, type, &res.f);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.f);
 			break;
 		case VT_DOUBLE:
 			res.d = f.call_d();
-			variable_set_from(v, type, &res.d);
+			if(result != NULL)
+				ret = variable_set_from(result, type, &res.d);
 			break;
 		default:
-			variable_delete(v);
-			return -1;
+			return -error_set_code(1, "%s", strerror(ENOSYS));
 	}
-	*result = v;
-	return 0;
+	return ret;
 }
diff --git a/src/marshall.h b/src/marshall.h
index 5b2ff9e..4292c04 100644
--- a/src/marshall.h
+++ b/src/marshall.h
@@ -23,7 +23,7 @@
 
 /* Marshall */
 /* functions */
-int marshall_call(VariableType type, Variable ** result, void * func,
+int marshall_call(VariableType type, Variable * result, void * func,
 		size_t argc, Variable ** argv);
 
 #endif /* !LIBAPP_MARSHALL_H */
diff --git a/tools/appclient.c b/tools/appclient.c
index aa08849..0726abe 100644
--- a/tools/appclient.c
+++ b/tools/appclient.c
@@ -91,7 +91,7 @@ static int _appclient(int verbose, char const * app, char const * name,
 static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 {
 	int ret = 0;
-	Variable * v = NULL;
+	Variable * v;
 	int res;
 
 #ifdef DEBUG
@@ -100,6 +100,8 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 	if(verbose != 0)
 		printf("Calling %s() with %lu arguments\n", call->name,
 				(unsigned long)call->args_cnt);
+	if((v = variable_new(VT_NULL, NULL)) == NULL)
+		return -1;
 	/* FIXME may segfault (check interface), use appclient_callv? */
 	switch(call->args_cnt)
 	{
@@ -108,7 +110,7 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 			fprintf(stderr, "DEBUG: %s() %s() res=%d\n", __func__,
 					call->name, res);
 #endif
-			ret = appclient_call(ac, &v, call->name, NULL);
+			ret = appclient_call_variable(ac, v, call->name, NULL);
 			break;
 		case 1:
 #ifdef DEBUG
@@ -116,16 +118,16 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 					call->name, call->args[0].integer);
 #endif
 			if(call->args[0].type == ACCAT_DOUBLE)
-				ret = appclient_call(ac, &v, call->name,
+				ret = appclient_call_variable(ac, v, call->name,
 						call->args[0]._double);
 			else if(call->args[0].type == ACCAT_FLOAT)
-				ret = appclient_call(ac, &v, call->name,
+				ret = appclient_call_variable(ac, v, call->name,
 						call->args[0]._float);
 			else if(call->args[0].type == ACCAT_INTEGER)
-				ret = appclient_call(ac, &v, call->name,
+				ret = appclient_call_variable(ac, v, call->name,
 						call->args[0].integer);
 			else if(call->args[0].type == ACCAT_STRING)
-				ret = appclient_call(ac, &v, call->name,
+				ret = appclient_call_variable(ac, v, call->name,
 						call->args[0].string);
 			else
 				ret = error_set_code(1, "%s",
@@ -139,7 +141,7 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 					call->args[0].integer,
 					call->args[1].integer);
 #endif
-			ret = appclient_call(ac, &v, call->name,
+			ret = appclient_call_variable(ac, v, call->name,
 					call->args[0].integer,
 					call->args[1].integer);
 			break;
@@ -154,7 +156,7 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 						call->args[1]._float,
 						call->args[2]._float);
 #endif
-				ret = appclient_call(ac, &v, call->name,
+				ret = appclient_call_variable(ac, v, call->name,
 						call->args[0]._float,
 						call->args[1]._float,
 						call->args[2]._float);
@@ -168,7 +170,7 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 					call->args[1].integer,
 					call->args[2].integer);
 #endif
-			ret = appclient_call(ac, &v, call->name,
+			ret = appclient_call_variable(ac, v, call->name,
 					call->args[0].integer,
 					call->args[1].integer,
 					call->args[2].integer);
@@ -182,7 +184,7 @@ static int _appclient_call(int verbose, AppClient * ac, AppClientCall * call)
 					call->args[2]._float,
 					call->args[3]._float);
 #endif
-			ret = appclient_call(ac, &v, call->name,
+			ret = appclient_call_variable(ac, v, call->name,
 					call->args[0]._float,
 					call->args[1]._float,
 					call->args[2]._float,