diff --git a/md5.c b/md5.c
index 781dbd1..3f8ad28 100644
--- a/md5.c
+++ b/md5.c
@@ -308,7 +308,7 @@ void md5_end(void *resbuf, md5_ctx_t *ctx)
 	memset(ctx, 0, sizeof(*ctx));
 }
 
-int md5sum(char *file, void *md5_buf)
+int md5sum(const char *file, void *md5_buf)
 {
 	char buf[256];
 	md5_ctx_t ctx;
diff --git a/md5.h b/md5.h
index b2f1b80..d3ee4e3 100644
--- a/md5.h
+++ b/md5.h
@@ -53,6 +53,6 @@ typedef struct md5_ctx {
 extern void md5_begin(md5_ctx_t *ctx);
 extern void md5_hash(const void *data, size_t length, md5_ctx_t *ctx);
 extern void md5_end(void *resbuf, md5_ctx_t *ctx);
-int md5sum(char *file, void *md5_buf);
+int md5sum(const char *file, void *md5_buf);
 
 #endif