diff --git a/pycardium/modules/os.c b/pycardium/modules/os.c
index cc4b067996e5c505cfa0a71f3ae9e478fc99ddfb..d8e6a105f0061e75afd0fae7bce2a8aa8d9e5b79 100644
--- a/pycardium/modules/os.c
+++ b/pycardium/modules/os.c
@@ -29,7 +29,7 @@ bool pycrd_filename_restricted(const char *path)
 	}
 	fname = path;
 
-	for (int i = 0;
+	for (size_t i = 0;
 	     i < sizeof(forbidden_files) / sizeof(forbidden_files[0]);
 	     i++) {
 		if (strcasecmp(fname, forbidden_files[i]) == 0) {
diff --git a/pycardium/modules/sys_display.c b/pycardium/modules/sys_display.c
index 387101a1594efeb7ee63e7373c6666b2b6a5a896..40ec6125bfef12132ab9cbe3ce6273b807131d37 100644
--- a/pycardium/modules/sys_display.c
+++ b/pycardium/modules/sys_display.c
@@ -120,7 +120,7 @@ static mp_obj_t mp_display_line(size_t n_args, const mp_obj_t *args)
 	uint16_t ls  = mp_obj_get_int(args[5]);
 	uint16_t ps  = mp_obj_get_int(args[6]);
 
-	if (ls > 1 || ls < 0) {
+	if (ls > 1) {
 		mp_raise_ValueError("Line style has to be 0 or 1");
 	}
 
@@ -145,7 +145,7 @@ static mp_obj_t mp_display_rect(size_t n_args, const mp_obj_t *args)
 	uint16_t fs  = mp_obj_get_int(args[5]);
 	uint16_t ps  = mp_obj_get_int(args[6]);
 
-	if (fs > 1 || fs < 0) {
+	if (fs > 1) {
 		mp_raise_ValueError("Fill style has to be 0 or 1");
 	}
 
@@ -169,7 +169,7 @@ static mp_obj_t mp_display_circ(size_t n_args, const mp_obj_t *args)
 	uint16_t fs  = mp_obj_get_int(args[4]);
 	uint16_t ps  = mp_obj_get_int(args[5]);
 
-	if (fs > 1 || fs < 0) {
+	if (fs > 1) {
 		mp_raise_ValueError("Fill style has to be 0 or 1");
 	}