diff --git a/lib/liboath/oath_base32.c b/lib/liboath/oath_base32.c
index 7f7bbc6..f95c87f 100644
--- a/lib/liboath/oath_base32.c
+++ b/lib/liboath/oath_base32.c
@@ -87,7 +87,7 @@ static const char b32dec[256] = {
 int
 base32_enc(const char *cin, size_t ilen, char *out, size_t *olen)
 {
-	const uint8_t *in = (uint8_t *)cin;
+	const uint8_t *in = (const uint8_t *)cin;
 	uint64_t bits;
 
 	if (*olen <= base32_enclen(ilen)) {
@@ -163,7 +163,7 @@ base32_enc(const char *cin, size_t ilen, char *out, size_t *olen)
 int
 base32_dec(const char *cin, size_t ilen, char *out, size_t *olen)
 {
-	const uint8_t *in = (uint8_t *)cin;
+	const uint8_t *in = (const uint8_t *)cin;
 	size_t len;
 	int bits, shift, padding;
 
diff --git a/lib/liboath/oath_base64.c b/lib/liboath/oath_base64.c
index 1ef9659..3c37ee1 100644
--- a/lib/liboath/oath_base64.c
+++ b/lib/liboath/oath_base64.c
@@ -89,7 +89,7 @@ static const char b64dec[256] = {
 int
 base64_enc(const char *cin, size_t ilen, char *out, size_t *olen)
 {
-	const uint8_t *in = (uint8_t *)cin;
+	const uint8_t *in = (const uint8_t *)cin;
 	uint32_t bits;
 
 	if (*olen <= base64_enclen(ilen)) {
@@ -151,7 +151,7 @@ base64_enc(const char *cin, size_t ilen, char *out, size_t *olen)
 int
 base64_dec(const char *cin, size_t ilen, char *out, size_t *olen)
 {
-	const uint8_t *in = (uint8_t *)cin;
+	const uint8_t *in = (const uint8_t *)cin;
 	size_t len;
 	int bits, shift, padding;
 
diff --git a/lib/liboath/oath_key.c b/lib/liboath/oath_key.c
index f053592..4eb99a8 100644
--- a/lib/liboath/oath_key.c
+++ b/lib/liboath/oath_key.c
@@ -93,7 +93,7 @@ oath_key_to_uri(const struct oath_key *key)
 		return (NULL);
 	}
 	uri = tmp;
-	if (base32_enc((char *)key->key, key->keylen, uri + urilen, &kslen) != 0) {
+	if (base32_enc((const char *)key->key, key->keylen, uri + urilen, &kslen) != 0) {
 		free(uri);
 		return (NULL);
 	}