diff --git a/docs/sim.html b/docs/sim.html
index ea37460..4f508d2 100644
--- a/docs/sim.html
+++ b/docs/sim.html
@@ -427,6 +427,7 @@ Turn on the phone and you will be asked for a PIN.
 Enter the PIN 9991 to alter the first subscriber data.
 Enter the PIN 9992 .. 9998 to alter second to eighth subscriber data.
 The subscriber data is shown in the telephone directory and can be altered by changing the numbers in that directory.
+The Bosch OF 7 does not like to store numbers less than 3 digits. Put zeroes in front, if you want to store a value less than 1000.
 </p>
 
 <p>
diff --git a/src/sim/sim.c b/src/sim/sim.c
index 086519e..b6446ae 100644
--- a/src/sim/sim.c
+++ b/src/sim/sim.c
@@ -31,7 +31,9 @@
 #ifdef ARDUINO
 #define LOGP(cat, level, fmt, arg...) while(0)
 #define EINVAL 22
-static uint32_t my_strtoul(const char *nptr, char **endptr, int base)
+#endif
+
+static uint32_t my_strtoul(const char *nptr, char __attribute__((unused)) **endptr, int __attribute__((unused)) base)
 {
 	uint32_t number = 0;
 
@@ -40,9 +42,6 @@ static uint32_t my_strtoul(const char *nptr, char **endptr, int base)
 
 	return number;
 }
-#else
-#define my_strtoul strtoul
-#endif
 
 static void my_ultostr(char *nptr, uint32_t value, int zeros)
 {
@@ -143,7 +142,7 @@ int encode_ebdt(uint8_t *data, const char *futln, const char *sicherung, const c
 			if (futln[i] < '0' || futln[i] > '9')
 				break;
 		}
-		temp = my_strtoul(futln, NULL, 0);
+		temp = my_strtoul(futln, NULL, 10);
 		if (i < 5 || temp > 65535) {
 			LOGP(DSIM7, LOGL_NOTICE, "Given FUTLN '%s' has invalid last digits. (Must be '00000' .. '65535')\n", futln);
 			return -EINVAL;
@@ -153,7 +152,7 @@ int encode_ebdt(uint8_t *data, const char *futln, const char *sicherung, const c
 	}
 
 	if (sicherung) {
-		temp = my_strtoul(sicherung, NULL, 0);
+		temp = my_strtoul(sicherung, NULL, 10);
 		if (temp > 65535) {
 			LOGP(DSIM7, LOGL_NOTICE, "Given security code '%s' has invalid digits. (Must be '0' .. '65535')\n", sicherung);
 			return -EINVAL;
@@ -163,7 +162,7 @@ int encode_ebdt(uint8_t *data, const char *futln, const char *sicherung, const c
 	}
 
 	if (karten) {
-		temp = my_strtoul(karten, NULL, 0);
+		temp = my_strtoul(karten, NULL, 10);
 		if (temp > 7) {
 			LOGP(DSIM7, LOGL_NOTICE, "Given card number '%s' has invalid digit. (Must be '0' .. '7')\n", karten);
 			return -EINVAL;
@@ -172,7 +171,7 @@ int encode_ebdt(uint8_t *data, const char *futln, const char *sicherung, const c
 	}
 
 	if (sonder) {
-		temp = my_strtoul(sonder, NULL, 0);
+		temp = my_strtoul(sonder, NULL, 10);
 		if (temp > 8191) {
 			LOGP(DSIM7, LOGL_NOTICE, "Given spacial code '%s' has invalid digits. (Must be '0' .. '8191')\n", sonder);
 			return -EINVAL;
@@ -182,7 +181,7 @@ int encode_ebdt(uint8_t *data, const char *futln, const char *sicherung, const c
 	}
 
 	if (wartung) {
-		temp = my_strtoul(wartung, NULL, 0);
+		temp = my_strtoul(wartung, NULL, 10);
 		if (temp > 65535) {
 			LOGP(DSIM7, LOGL_NOTICE, "Given maintenance code '%s' has invalid digits. (Must be '0' .. '65535')\n", wartung);
 			return -EINVAL;