diff --git a/util/nvmutil/nvmutil.c b/util/nvmutil/nvmutil.c
index 77b33aa2..38d34436 100644
--- a/util/nvmutil/nvmutil.c
+++ b/util/nvmutil/nvmutil.c
@@ -141,9 +141,12 @@ rhex(void)
 {
 	static int rfd = -1, n = 0;
 	static uint8_t rnum[16];
-	xopen(rfd, "/dev/urandom", O_RDONLY);
-	if (!n)
+	if (!n) {
+		if (rfd == -1) {
+			xopen(rfd, "/dev/urandom", O_RDONLY);
+		}
 		xpread(rfd, (uint8_t *) &rnum, (n = 15) + 1, 0, "/dev/urandom");
+	}
 	return rnum[n--] & 0xf;
 }
 
diff --git a/util/nvmutil/nvmutil.h b/util/nvmutil/nvmutil.h
index 1b928a34..043e0f39 100644
--- a/util/nvmutil/nvmutil.h
+++ b/util/nvmutil/nvmutil.h
@@ -51,9 +51,7 @@ int big_endian;
 #define ERR() errno = errno ? errno : ECANCELED
 #define err_if(x) if (x) err(ERR(), NULL)
 
-#define xopen(f,l,p) \
-	if (f == -1) \
-	if (opendir(l) != NULL) err(errno = EISDIR, "%s", l); \
+#define xopen(f,l,p) if (opendir(l) != NULL) err(errno = EISDIR, "%s", l); \
 	if ((f = open(l, p)) == -1) err(ERR(), "%s", l); \
 	struct stat st; if (fstat(f, &st) == -1) err(ERR(), "%s", l)
 #define xpread(f, b, n, o, l) if (pread(f, b, n, o) == -1) err(ERR(), "%s", l)