diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 8064f63639..ab2b006ae4 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -8492,7 +8492,7 @@ zfs_do_wait(int argc, char **argv)
 {
 	boolean_t enabled[ZFS_WAIT_NUM_ACTIVITIES];
 	int error, i;
-	char c;
+	int c;
 
 	/* By default, wait for all types of activity. */
 	for (i = 0; i < ZFS_WAIT_NUM_ACTIVITIES; i++)
diff --git a/cmd/zfs_ids_to_path/zfs_ids_to_path.c b/cmd/zfs_ids_to_path/zfs_ids_to_path.c
index 6cfaa6f41f..80dd5bf2dc 100644
--- a/cmd/zfs_ids_to_path/zfs_ids_to_path.c
+++ b/cmd/zfs_ids_to_path/zfs_ids_to_path.c
@@ -44,7 +44,7 @@ int
 main(int argc, char **argv)
 {
 	boolean_t verbose = B_FALSE;
-	char c;
+	int c;
 	while ((c = getopt(argc, argv, "v")) != -1) {
 		switch (c) {
 		case 'v':
diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index c84f30ccb1..e00fdb7ae1 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -10147,7 +10147,7 @@ int
 zpool_do_wait(int argc, char **argv)
 {
 	boolean_t verbose = B_FALSE;
-	char c;
+	int c;
 	char *value;
 	int i;
 	unsigned long count;
diff --git a/cmd/zstream/zstream_redup.c b/cmd/zstream/zstream_redup.c
index 379025ce59..41f1068e3d 100644
--- a/cmd/zstream/zstream_redup.c
+++ b/cmd/zstream/zstream_redup.c
@@ -421,7 +421,7 @@ int
 zstream_do_redup(int argc, char *argv[])
 {
 	boolean_t verbose = B_FALSE;
-	char c;
+	int c;
 
 	while ((c = getopt(argc, argv, "v")) != -1) {
 		switch (c) {
diff --git a/tests/zfs-tests/cmd/btree_test/btree_test.c b/tests/zfs-tests/cmd/btree_test/btree_test.c
index e1995c03af..8de14ff2a2 100644
--- a/tests/zfs-tests/cmd/btree_test/btree_test.c
+++ b/tests/zfs-tests/cmd/btree_test/btree_test.c
@@ -457,7 +457,7 @@ main(int argc, char *argv[])
 	int failed_tests = 0;
 	struct timeval tp;
 	zfs_btree_t bt;
-	char c;
+	int c;
 
 	while ((c = getopt(argc, argv, "c:l:n:r:st:")) != -1) {
 		switch (c) {