diff --git a/Grow.c b/Grow.c
index 65b708a..29d3628 100644
--- a/Grow.c
+++ b/Grow.c
@@ -512,8 +512,21 @@ int Grow_reshape(char *devname, int fd, int quiet, char *backup_file,
 			}
 		}
 		if (size >= 0) {
+			int rv;
 			array.size = size;
-			if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
+			if (array.size != size) {
+				/* got truncated to 32bit, write to
+				 * component_size instead
+				 */
+				sra = sysfs_read(fd, 0, 0);
+				if (sra)
+					rv = sysfs_set_num(sra, NULL,
+							   "component_size", size);
+				else
+					rv = -1;
+			} else
+				rv = ioctl(fd, SET_ARRAY_INFO, &array);
+			if (rv != 0) {
 				fprintf(stderr, Name ": Cannot set device size for %s: %s\n",
 					devname, strerror(errno));
 				return 1;
diff --git a/mdadm.c b/mdadm.c
index 0432622..a77c4ad 100644
--- a/mdadm.c
+++ b/mdadm.c
@@ -389,12 +389,14 @@ int main(int argc, char *argv[])
 			if (strcmp(optarg, "max")==0)
 				size = 0;
 			else {
-				size = strtoll(optarg, &c, 10);
-				if (!optarg[0] || *c || size < 4) {
+				size = parse_size(optarg);
+				if (size < 8) {
 					fprintf(stderr, Name ": invalid size: %s\n",
 						optarg);
 					exit(2);
 				}
+				/* convert sectors to K */
+				size /= 2;
 			}
 			continue;