diff --git a/library/pkcs7.c b/library/pkcs7.c
index 2cc7812bf0..61e9ee9754 100644
--- a/library/pkcs7.c
+++ b/library/pkcs7.c
@@ -142,6 +142,10 @@ static int pkcs7_get_digest_algorithm_set(unsigned char **p,
         return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_PKCS7_INVALID_ALG, ret);
     }
 
+    if (len == 0) {
+        return 0;
+    }
+
     end = *p + len;
 
     ret = mbedtls_asn1_get_alg_null(p, end, alg);
@@ -481,9 +485,11 @@ static int pkcs7_get_signed_data(unsigned char *buf, size_t buflen,
         return ret;
     }
 
-    ret = mbedtls_x509_oid_get_md_alg(&signed_data->digest_alg_identifiers, &md_alg);
-    if (ret != 0) {
-        return MBEDTLS_ERR_PKCS7_INVALID_ALG;
+    if (signed_data->digest_alg_identifiers.p != NULL) {
+        ret = mbedtls_x509_oid_get_md_alg(&signed_data->digest_alg_identifiers, &md_alg);
+        if (ret != 0) {
+           return MBEDTLS_ERR_PKCS7_INVALID_ALG;
+        }
     }
 
     mbedtls_pkcs7_buf content_type;