diff --git a/libdm/dm-tools/dmsetup.c b/libdm/dm-tools/dmsetup.c
index f6d1ecf90..0f260b3f4 100644
--- a/libdm/dm-tools/dmsetup.c
+++ b/libdm/dm-tools/dmsetup.c
@@ -6680,7 +6680,7 @@ static int _process_losetup_switches(const char *base, int *argcp, char ***argvp
 	};
 #endif
 
-	optarg = 0;
+	optarg = (char*) "";
 	optind = OPTIND_INIT;
 	while ((c = GETOPTLONG_FN(*argcp, *argvp, "ade:fo:v",
 				  long_options, NULL)) != -1 ) {
@@ -6976,7 +6976,7 @@ static int _process_switches(int *argcp, char ***argvp, const char *dev_dir)
 		return r;
 	}
 
-	optarg = 0;
+	optarg = (char*) "";
 	optind = OPTIND_INIT;
 	while ((ind = -1, c = GETOPTLONG_FN(*argcp, *argvp, "cCfG:hj:m:M:no:O:rS:u:U:vy",
 					    long_options, NULL)) != -1) {
diff --git a/tools/lvmcmdline.c b/tools/lvmcmdline.c
index de70e63c9..7c5930006 100644
--- a/tools/lvmcmdline.c
+++ b/tools/lvmcmdline.c
@@ -2236,7 +2236,7 @@ static int _process_command_line(struct cmd_context *cmd, int *argc, char ***arg
 	*ptr = '\0';
 	memset(o, 0, sizeof(*o));
 
-	optarg = 0;
+	optarg = (char*) "";
 	optind = OPTIND_INIT;
 	while ((goval = GETOPTLONG_FN(*argc, *argv, str, opts, NULL)) >= 0) {