diff --git a/src/lib/ebus/device.cpp b/src/lib/ebus/device.cpp
index a949746d..310c4a52 100644
--- a/src/lib/ebus/device.cpp
+++ b/src/lib/ebus/device.cpp
@@ -50,7 +50,7 @@ Device* Device::create(const char* name, const bool checkDevice, const bool read
 		if (pos != NULL) {
 			char* end = NULL;
 			unsigned long int port = strtoul(pos+1, &end, 10);
-			if (end == NULL || *end != 0 || port < 1 || port > 65535) {
+			if (end == NULL || end == pos+1 || *end != 0 || port < 1 || port > 65535) {
 				return NULL; // invalid port
 			}
 			struct sockaddr_in address;
diff --git a/src/tools/ebusctl.cpp b/src/tools/ebusctl.cpp
index 150e5b49..9d63a722 100644
--- a/src/tools/ebusctl.cpp
+++ b/src/tools/ebusctl.cpp
@@ -102,7 +102,7 @@ error_t parse_opt(int key, char *arg, struct argp_state *state)
 		break;
 	case 'p': // --port=8888
 		port = strtoul(arg, &strEnd, 10);
-		if (strEnd == NULL || *strEnd != 0 || port < 1 || port > 65535) {
+		if (strEnd == NULL || strEnd == arg || *strEnd != 0 || port < 1 || port > 65535) {
 			argp_error(state, "invalid port");
 			return EINVAL;
 		}
diff --git a/src/tools/ebusfeed.cpp b/src/tools/ebusfeed.cpp
index 79c1d039..d1f532e8 100644
--- a/src/tools/ebusfeed.cpp
+++ b/src/tools/ebusfeed.cpp
@@ -102,7 +102,7 @@ error_t parse_opt(int key, char *arg, struct argp_state *state)
 		break;
 	case 't': // --time=10000
 		opt->time = (unsigned int)strtoul(arg, &strEnd, 10);
-		if (strEnd == NULL || *strEnd != 0 || opt->time < 1000 || opt->time > 100000000) {
+		if (strEnd == NULL || strEnd == arg || *strEnd != 0 || opt->time < 1000 || opt->time > 100000000) {
 			argp_error(state, "invalid time");
 			return EINVAL;
 		}