diff --git a/OpenSSL/crypto/crypto.c b/OpenSSL/crypto/crypto.c
index 87f3e75..a81773d 100644
--- a/OpenSSL/crypto/crypto.c
+++ b/OpenSSL/crypto/crypto.c
@@ -24,6 +24,18 @@
 
 PyObject *crypto_Error;
 
+int crypto_byte_converter(PyObject *input, void* output) {
+    char **message = output;
+    if (input == Py_None) {
+        *message = NULL;
+    } else if (PyBytes_CheckExact(input)) {
+        *message = PyBytes_AsString(input);
+    } else {
+        return 0;
+    }
+    return 1;
+}
+
 static int
 global_passphrase_callback(char *buf, int len, int rwflag, void *cb_arg)
 {
@@ -612,8 +624,9 @@
     EVP_MD_CTX md_ctx;
     unsigned char sig_buf[512];
 
-    if (!PyArg_ParseTuple(args, "O!ss:sign", &crypto_PKey_Type,
-                          &pkey, &data, &digest_name)) {
+    if (!PyArg_ParseTuple(
+            args, "O!" BYTESTRING_FMT BYTESTRING_FMT ":sign", &crypto_PKey_Type,
+            &pkey, &data, &digest_name)) {
         return NULL;
     }
 
@@ -657,8 +670,11 @@
     EVP_MD_CTX md_ctx;
     EVP_PKEY *pkey;
 
-    if (!PyArg_ParseTuple(args, "O!t#ss:verify", &crypto_X509_Type, &cert, &signature, &sig_len,
-                          &data, &digest_name)) {
+#ifdef PY3
+    if (!PyArg_ParseTuple(args, "O!y#yy:verify", &crypto_X509_Type, &cert, &signature, &sig_len, &data, &digest_name)) {
+#else
+    if (!PyArg_ParseTuple(args, "O!t#ss:verify", &crypto_X509_Type, &cert, &signature, &sig_len, &data, &digest_name)) {
+#endif
         return NULL;
     }
 
diff --git a/OpenSSL/crypto/crypto.h b/OpenSSL/crypto/crypto.h
index 9b9663d..75961a7 100644
--- a/OpenSSL/crypto/crypto.h
+++ b/OpenSSL/crypto/crypto.h
@@ -74,6 +74,8 @@
 extern crypto_PKCS7_New_RETURN     crypto_PKCS7_New     crypto_PKCS7_New_PROTO;
 extern crypto_NetscapeSPKI_New_RETURN  crypto_NetscapeSPKI_New  crypto_NetscapeSPKI_New_PROTO;
 
+int crypto_byte_converter(PyObject *input, void *output);
+
 #else /* crypto_MODULE */
 
 extern void **crypto_API;
diff --git a/OpenSSL/crypto/revoked.c b/OpenSSL/crypto/revoked.c
index c876373..e9b1297 100644
--- a/OpenSSL/crypto/revoked.c
+++ b/OpenSSL/crypto/revoked.c
@@ -123,19 +123,6 @@
 }
 
 
-static int
-crypto_byte_converter(PyObject *input, void* output) {
-    char **message = output;
-    if (input == Py_None) {
-        *message = NULL;
-    } else if (PyBytes_CheckExact(input)) {
-        *message = PyBytes_AsString(input);
-    } else {
-        return 0;
-    }
-    return 1;
-}
-
 static char crypto_Revoked_set_reason_doc[] = "\n\
 Set the reason of a Revoked object.\n\
 \n\