diff --git a/cmd.c b/cmd.c
index 004330d..0b8513e 100644
--- a/cmd.c
+++ b/cmd.c
@@ -292,7 +292,7 @@ int
 ftp_cmd_CHMOD(ftp_env_t *env, const char* arg) {
   char pathbuf[PATH_MAX];
   mode_t mode = 0;
-  char* ptr;
+  const char* ptr;
 
   if(!arg[0] || !(ptr=strstr(arg, " "))) {
     return ftp_active_printf(env, "501 Usage: CHMOD <MODE> <PATH>\r\n");
diff --git a/main-linux.c b/main-linux.c
index a7d8445..d4b1b74 100644
--- a/main-linux.c
+++ b/main-linux.c
@@ -28,7 +28,7 @@ main(int argc, char* argv[]) {
   int notify_user = 1;
   char c;
 
-  while((c=getopt(argc, argv, "p:h")) != -1) {
+  while((c=getopt(argc, argv, "p:h")) != (char)-1) {
     switch(c) {
     case 'p':
       port = atoi(optarg);
diff --git a/main-orbis.c b/main-orbis.c
index 5fc9e11..8ff2afe 100644
--- a/main-orbis.c
+++ b/main-orbis.c
@@ -84,7 +84,7 @@ main(int argc, char* argv[]) {
 
   syscall(SYS_thr_set_name, -1, "ftpsrv.elf");
 
-  while((c=getopt(argc, argv, "p:qh")) != -1) {
+  while((c=getopt(argc, argv, "p:qh")) != (char)-1) {
     switch(c) {
     case 'p':
       port = atoi(optarg);
diff --git a/main-prospero.c b/main-prospero.c
index 43d7d13..667c34c 100644
--- a/main-prospero.c
+++ b/main-prospero.c
@@ -85,7 +85,7 @@ main(int argc, char* argv[]) {
 
   syscall(SYS_thr_set_name, -1, "ftpsrv.elf");
 
-  while((c=getopt(argc, argv, "p:qh")) != -1) {
+  while((c=getopt(argc, argv, "p:qh")) != (char)-1) {
     switch(c) {
     case 'p':
       port = atoi(optarg);