diff --git a/c_src/xav/reader.c b/c_src/xav/reader.c
index 9617227..6007652 100644
--- a/c_src/xav/reader.c
+++ b/c_src/xav/reader.c
@@ -2,7 +2,7 @@
 #include "utils.h"
 #include <libavutil/version.h>
 
-int reader_init(struct Reader *reader, char *path, size_t path_size, int device_flag,
+int reader_init(struct Reader *reader, unsigned char *path, size_t path_size, int device_flag,
                 enum AVMediaType media_type) {
   int ret;
   reader->path = XAV_ALLOC(path_size + 1);
diff --git a/c_src/xav/reader.h b/c_src/xav/reader.h
index 3226a42..6a7a31d 100644
--- a/c_src/xav/reader.h
+++ b/c_src/xav/reader.h
@@ -41,7 +41,7 @@ struct Reader {
   int *frame_linesize;
 };
 
-int reader_init(struct Reader *reader, char *path, size_t path_size, int device_flag,
+int reader_init(struct Reader *reader, unsigned char *path, size_t path_size, int device_flag,
                 enum AVMediaType media_type);
 
 int reader_next_frame(struct Reader *reader);
diff --git a/c_src/xav/xav_nif.c b/c_src/xav/xav_nif.c
index f3f1c56..f643771 100644
--- a/c_src/xav/xav_nif.c
+++ b/c_src/xav/xav_nif.c
@@ -109,7 +109,7 @@ ERL_NIF_TERM new_decoder(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
 
   struct Decoder *decoder = enif_alloc_resource(decoder_resource_type, sizeof(struct Decoder));
 
-  int codec_len;
+  unsigned int codec_len;
   if (!enif_get_atom_length(env, argv[0], &codec_len, ERL_NIF_LATIN1)) {
     return xav_nif_raise(env, "failed_to_get_atom_length");
   }