diff --git a/crypto/asn1/asn_pack.c b/crypto/asn1/asn_pack.c
index 1f5be531896f6056cedb8cd36a23f7c4f672d72e..63bc30675655fc69ff32212a8443234a51e400d9 100644
--- a/crypto/asn1/asn_pack.c
+++ b/crypto/asn1/asn_pack.c
@@ -50,7 +50,7 @@ ASN1_STRING *ASN1_item_pack(void *obj, const ASN1_ITEM *it, ASN1_STRING **oct)
 
 /* Extract an ASN1 object from an ASN1_STRING */
 
-void *ASN1_item_unpack(ASN1_STRING *oct, const ASN1_ITEM *it)
+void *ASN1_item_unpack(const ASN1_STRING *oct, const ASN1_ITEM *it)
 {
     const unsigned char *p;
     void *ret;
diff --git a/include/openssl/asn1.h b/include/openssl/asn1.h
index 40526fbaa23617a9ab0e072de17af96026529114..d37a3fc79385a690458818db2cd91ea8af97fc53 100644
--- a/include/openssl/asn1.h
+++ b/include/openssl/asn1.h
@@ -772,7 +772,7 @@ int ASN1_TYPE_set_int_octetstring(ASN1_TYPE *a, long num,
 int ASN1_TYPE_get_int_octetstring(const ASN1_TYPE *a, long *num,
                                   unsigned char *data, int max_len);
 
-void *ASN1_item_unpack(ASN1_STRING *oct, const ASN1_ITEM *it);
+void *ASN1_item_unpack(const ASN1_STRING *oct, const ASN1_ITEM *it);
 
 ASN1_STRING *ASN1_item_pack(void *obj, const ASN1_ITEM *it,
                             ASN1_OCTET_STRING **oct);