diff --git a/src/iscsi-inq.c b/src/iscsi-inq.c
index c38718d..56e4903 100644
--- a/src/iscsi-inq.c
+++ b/src/iscsi-inq.c
@@ -302,7 +302,9 @@ int main(int argc, char *argv[])
 		iscsi_set_log_fn(iscsi, iscsi_log_to_stderr);
 	}
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify the URL\n");
 		print_usage();
diff --git a/src/iscsi-ls.c b/src/iscsi-ls.c
index e17a55d..b9441ef 100644
--- a/src/iscsi-ls.c
+++ b/src/iscsi-ls.c
@@ -380,7 +380,9 @@ int main(int argc, char *argv[])
 
 	memset(&state, 0, sizeof(state));
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify iscsi target portal.\n");
 		print_usage();
diff --git a/src/iscsi-readcapacity16.c b/src/iscsi-readcapacity16.c
index 5bb34db..8749088 100644
--- a/src/iscsi-readcapacity16.c
+++ b/src/iscsi-readcapacity16.c
@@ -125,7 +125,9 @@ int main(int argc, char *argv[])
 		iscsi_set_log_level(iscsi, debug);
 	}
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify the URL\n");
 		print_usage();
diff --git a/src/iscsi-swp.c b/src/iscsi-swp.c
index bc1721f..44607e4 100644
--- a/src/iscsi-swp.c
+++ b/src/iscsi-swp.c
@@ -138,7 +138,9 @@ int main(int argc, char *argv[])
 		iscsi_set_log_fn(iscsi, iscsi_log_to_stderr);
 	}
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify the URL\n");
 		print_usage();
diff --git a/test-tool/iscsi-test.c b/test-tool/iscsi-test.c
index dcf32a4..8723c06 100644
--- a/test-tool/iscsi-test.c
+++ b/test-tool/iscsi-test.c
@@ -396,7 +396,9 @@ int main(int argc, char *argv[])
 		exit(0);
 	}
 
-	url = strdup(argv[optind]);
+	if (argv[optind] != NULL) {
+		url = strdup(argv[optind]);
+	}
 	if (url == NULL) {
 		fprintf(stderr, "You must specify the URL\n");
 		print_usage();