diff --git a/thin-provisioning/thin_ll_dump.cc b/thin-provisioning/thin_ll_dump.cc
index f16a745..94f6a08 100644
--- a/thin-provisioning/thin_ll_dump.cc
+++ b/thin-provisioning/thin_ll_dump.cc
@@ -330,7 +330,7 @@ thin_ll_dump_cmd::run(int argc, char **argv)
 	boost::optional<string> output;
 	flags f;
 
-	char c;
+	int c;
 	while ((c = getopt_long(argc, argv, shortopts, longopts, NULL)) != -1) {
 		switch(c) {
 		case 'h':
diff --git a/thin-provisioning/thin_ll_restore.cc b/thin-provisioning/thin_ll_restore.cc
index ee1d88f..4082e0b 100644
--- a/thin-provisioning/thin_ll_restore.cc
+++ b/thin-provisioning/thin_ll_restore.cc
@@ -216,7 +216,7 @@ thin_ll_restore_cmd::run(int argc, char **argv) {
 	string output;
 	string input_metadata;
 	flags f;
-	char c;
+	int c;
 
 	const char shortopts[] = "hi:o:E:V";
 	const struct option longopts[] = {
diff --git a/thin-provisioning/thin_scan.cc b/thin-provisioning/thin_scan.cc
index 1ed7a6b..6f63df0 100644
--- a/thin-provisioning/thin_scan.cc
+++ b/thin-provisioning/thin_scan.cc
@@ -383,7 +383,7 @@ thin_scan_cmd::run(int argc, char **argv)
 	boost::optional<string> output;
 	flags f;
 
-	char c;
+	int c;
 	while ((c = getopt_long(argc, argv, shortopts, longopts, NULL)) != -1) {
 		switch(c) {
 		case 'h':