diff --git a/Makefile b/Makefile
index 52fc970..a152756 100644
--- a/Makefile
+++ b/Makefile
@@ -154,6 +154,7 @@ dist:
 		$(PACKAGE)-$(VERSION)/src/plugins/48x48/project.conf \
 		$(PACKAGE)-$(VERSION)/tests/modems.c \
 		$(PACKAGE)-$(VERSION)/tests/plugins.c \
+		$(PACKAGE)-$(VERSION)/tests/ussd.c \
 		$(PACKAGE)-$(VERSION)/tests/Makefile \
 		$(PACKAGE)-$(VERSION)/tests/tests.sh \
 		$(PACKAGE)-$(VERSION)/tests/project.conf \
diff --git a/src/modems/hayes.c b/src/modems/hayes.c
index 70b1145..e87791c 100644
--- a/src/modems/hayes.c
+++ b/src/modems/hayes.c
@@ -1,5 +1,5 @@
 /* $Id$ */
-/* Copyright (c) 2011-2013 Pierre Pronchery <khorben@defora.org> */
+/* Copyright (c) 2011-2014 Pierre Pronchery <khorben@defora.org> */
 /* This file is part of DeforaOS Desktop Phone */
 /* This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -371,6 +371,7 @@ static void _on_code_ext_error(ModemPlugin * modem, char const * answer);
 /* helpers */
 static int _is_figure(int c);
 static int _is_number(char const * number);
+static int _is_ussd_code(char const * number);
 
 
 /* variables */
@@ -759,8 +760,6 @@ static char * _request_attention(ModemPlugin * modem, ModemRequest * request)
 {
 	unsigned int type = request->type;
 	char buf[32];
-	char const * p;
-	size_t len;
 
 	switch(type)
 	{
@@ -784,9 +783,7 @@ static char * _request_attention(ModemPlugin * modem, ModemRequest * request)
 			break;
 		case MODEM_REQUEST_CALL:
 			if(request->call.call_type == MODEM_CALL_TYPE_VOICE
-					&& (p = request->call.number) != NULL
-					&& (len = strlen(p)) > 2
-					&& p[0] == '*' && p[len - 1] == '#')
+					&& _is_ussd_code(request->call.number))
 				return _request_attention_call_ussd(modem,
 						request);
 			return _request_attention_call(modem, request);
@@ -4086,3 +4083,19 @@ static int _is_number(char const * number)
 			return 0;
 	return 1;
 }
+
+
+/* is_ussd_code */
+static int _is_ussd_code(char const * number)
+{
+	if(number == NULL || number[0] != '*')
+		return 0;
+	for(number++; *number != '\0'; number++)
+		if((*number >= '0' && *number <= '9') || *number == '*')
+			continue;
+		else if(*number == '#' && *(number + 1) == '\0')
+			return 1;
+		else
+			return 0;
+	return 0;
+}
diff --git a/tests/Makefile b/tests/Makefile
index 5bde50e..35e5f8e 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -1,4 +1,4 @@
-TARGETS	= modems plugins tests.log
+TARGETS	= modems plugins ussd tests.log
 PREFIX	= /usr/local
 DESTDIR	=
 BINDIR	= $(PREFIX)/bin
@@ -31,7 +31,14 @@ plugins_LDFLAGS = $(LDFLAGSF) $(LDFLAGS)
 plugins: $(plugins_OBJS)
 	$(CC) -o plugins $(plugins_OBJS) $(plugins_LDFLAGS)
 
-tests.log: modems plugins tests.sh
+ussd_OBJS = ussd.o
+ussd_CFLAGS = $(CPPFLAGSF) $(CPPFLAGS) $(CFLAGSF) $(CFLAGS)
+ussd_LDFLAGS = $(LDFLAGSF) $(LDFLAGS)
+
+ussd: $(ussd_OBJS)
+	$(CC) -o ussd $(ussd_OBJS) $(ussd_LDFLAGS)
+
+tests.log: modems plugins tests.sh ussd
 	./tests.sh -P "$(PREFIX)" -- "tests.log"
 
 modems.o: modems.c
@@ -40,8 +47,11 @@ modems.o: modems.c
 plugins.o: plugins.c
 	$(CC) $(plugins_CFLAGS) -c plugins.c
 
+ussd.o: ussd.c ../src/modems/hayes.c
+	$(CC) $(ussd_CFLAGS) -c ussd.c
+
 clean:
-	$(RM) -- $(modems_OBJS) $(plugins_OBJS) $(tests.log_OBJS)
+	$(RM) -- $(modems_OBJS) $(plugins_OBJS) $(ussd_OBJS) $(tests.log_OBJS)
 	./tests.sh -c -P "$(PREFIX)" -- "tests.log"
 
 distclean: clean
diff --git a/tests/project.conf b/tests/project.conf
index a5cbd65..b4e338e 100644
--- a/tests/project.conf
+++ b/tests/project.conf
@@ -1,4 +1,4 @@
-targets=modems,plugins,tests.log
+targets=modems,plugins,ussd,tests.log
 cppflags_force=-I ../include
 cflags_force=-W `pkg-config --cflags libDesktop`
 cflags=-Wall -g -O2
@@ -16,4 +16,11 @@ sources=plugins.c
 [tests.log]
 type=script
 script=./tests.sh
-depends=modems,plugins,tests.sh
+depends=modems,plugins,tests.sh,ussd
+
+[ussd]
+type=binary
+sources=ussd.c
+
+[ussd.c]
+depends=../src/modems/hayes.c
diff --git a/tests/tests.sh b/tests/tests.sh
index a41acf1..4ec087b 100755
--- a/tests/tests.sh
+++ b/tests/tests.sh
@@ -98,7 +98,7 @@ target="$1"
 $DATE > "$target"
 FAILED=
 echo "Performing tests:" 1>&2
-#_test "plugins"
+_test "ussd"
 echo "Expected failures:" 1>&2
 _fail "modems"
 _fail "plugins"
diff --git a/tests/ussd.c b/tests/ussd.c
new file mode 100644
index 0000000..419f811
--- /dev/null
+++ b/tests/ussd.c
@@ -0,0 +1,59 @@
+/* $Id$ */
+/* Copyright (c) 2014 Pierre Pronchery <khorben@defora.org> */
+/* This file is part of DeforaOS Desktop Phone */
+/* This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>. */
+
+
+
+#include "../src/modems/hayes.c"
+
+
+/* private */
+/* prototypes */
+static int _ussd(void);
+
+
+/* functions */
+/* ussd */
+static int _ussd(void)
+{
+	int ret = 0;
+	const char * codes[] = { "*100#" };
+	const char * notcodes[] = { "*#06#" };
+	size_t i;
+
+	for(i = 0; i < sizeof(codes) / sizeof(*codes); i++)
+		if(!_is_ussd_code(codes[i]))
+		{
+			printf("%s: %s: %s\n", "ussd", codes[i],
+					"Is a valid USSD code");
+			ret = 2;
+		}
+	for(i = 0; i < sizeof(notcodes) / sizeof(*notcodes); i++)
+		if(_is_ussd_code(notcodes[i]))
+		{
+			printf("%s: %s: %s\n", "ussd", notcodes[i],
+					"Is not a valid USSD code");
+			ret = 2;
+		}
+	return ret;
+}
+
+
+/* public */
+/* functions */
+/* main */
+int main(void)
+{
+	return (_ussd() == 0) ? 0 : 2;
+}