diff --git a/tool/openssl-compat.c b/tool/openssl-compat.c
index a51af90..bb37dfc 100644
--- a/tool/openssl-compat.c
+++ b/tool/openssl-compat.c
@@ -8,7 +8,7 @@
  */
 
 #include "openssl-compat.h"
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
 
 #include <string.h>
 #include <openssl/engine.h>
@@ -80,4 +80,4 @@ void X509_SIG_getm(X509_SIG *sig, X509_ALGOR **palg,
         *pdigest = sig->digest;
 }
 
-#endif /* OPENSSL_VERSION_NUMBER */
+#endif /* OPENSSL_VERSION_NUMBER || LIBRESSL_VERSION_NUMBER */
diff --git a/tool/openssl-compat.h b/tool/openssl-compat.h
index 3700bea..bd1967b 100644
--- a/tool/openssl-compat.h
+++ b/tool/openssl-compat.h
@@ -13,7 +13,7 @@
 #ifndef _WINDOWS
 
 #include <openssl/opensslv.h>
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
 
 #include <openssl/rsa.h>
 #include <openssl/dsa.h>
@@ -33,5 +33,5 @@ void X509_SIG_getm(X509_SIG *sig, X509_ALGOR **palg,
                    ASN1_OCTET_STRING **pdigest);
 
 #endif /* _WINDOWS */
-#endif /* OPENSSL_VERSION_NUMBER */
+#endif /* OPENSSL_VERSION_NUMBER || LIBRESSL_VERSION_NUMBER */
 #endif /* LIBCRYPTO_COMPAT_H */
diff --git a/tool/yubico-piv-tool.c b/tool/yubico-piv-tool.c
index 89daa79..c8b3b84 100644
--- a/tool/yubico-piv-tool.c
+++ b/tool/yubico-piv-tool.c
@@ -124,7 +124,7 @@ static bool sign_data(ykpiv_state *state, const unsigned char *in, size_t len, u
   return false;
 }
 
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+#if !((OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER))
 static int ec_key_ex_data_idx = -1;
 
 struct internal_key {
@@ -688,7 +688,7 @@ static bool request_certificate(ykpiv_state *state, enum enum_key_format key_for
     goto request_out;
   }
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
   memcpy(digest, oid, oid_len);
   /* XXX: this should probably use X509_REQ_digest() but that's buggy */
   if(!ASN1_item_digest(ASN1_ITEM_rptr(X509_REQ_INFO), md, req->req_info,
@@ -751,7 +751,7 @@ request_out:
     EVP_PKEY_free(public_key);
   }
   if(req) {
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
     if(req->sig_alg->parameter) {
       req->sig_alg->parameter = NULL;
     }
@@ -884,7 +884,7 @@ static bool selfsign_certificate(ykpiv_state *state, enum enum_key_format key_fo
   if(nid == 0) {
     goto selfsign_out;
   }
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
   if(YKPIV_IS_RSA(algorithm)) {
     signinput = digest;
     len = oid_len + md_len;
@@ -941,7 +941,7 @@ selfsign_out:
     fclose(output_file);
   }
   if(x509) {
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
     if(x509->sig_alg->parameter) {
       x509->sig_alg->parameter = NULL;
       x509->cert_info->signature->parameter = NULL;
diff --git a/ykcs11/openssl_utils.c b/ykcs11/openssl_utils.c
index 68fb29a..5a7f85d 100644
--- a/ykcs11/openssl_utils.c
+++ b/ykcs11/openssl_utils.c
@@ -165,7 +165,7 @@ CK_RV do_create_empty_cert(CK_BYTE_PTR in, CK_ULONG in_len, CK_BBOOL is_rsa,
   X509_set_notBefore(cert, tm);
   X509_set_notAfter(cert, tm);
 
-#if OPENSSL_VERSION_NUMBER < 10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
   // Manually set the signature algorithms.
   // OpenSSL 1.0.1i complains about empty DER fields
   // 8 => md5WithRsaEncryption
diff --git a/ykcs11/tests/ykcs11_tests.c b/ykcs11/tests/ykcs11_tests.c
index 9fb51da..257c938 100644
--- a/ykcs11/tests/ykcs11_tests.c
+++ b/ykcs11/tests/ykcs11_tests.c
@@ -274,7 +274,7 @@ static void test_login() {
 
 }
 
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+#if !((OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER))
 static int bogus_sign(int dtype, const unsigned char *m, unsigned int m_length,
                unsigned char *sigret, unsigned int *siglen, const RSA *rsa) {
   sigret = malloc(1);
@@ -385,7 +385,7 @@ static void test_import_and_sign_all_10() {
   X509_set_notBefore(cert, tm);
   X509_set_notAfter(cert, tm);
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
   cert->sig_alg->algorithm = OBJ_nid2obj(8);
   cert->cert_info->signature->algorithm = OBJ_nid2obj(8);
 
@@ -583,7 +583,7 @@ static void test_import_and_sign_all_10_RSA() {
   X509_set_notBefore(cert, tm);
   X509_set_notAfter(cert, tm);
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) || defined(LIBRESSL_VERSION_NUMBER)
   /* putting bogus data to signature to make some checks happy */
   cert->sig_alg->algorithm = OBJ_nid2obj(8);
   cert->cert_info->signature->algorithm = OBJ_nid2obj(8);