diff --git a/src/client.c b/src/client.c
index 21fa273..e500d62 100644
--- a/src/client.c
+++ b/src/client.c
@@ -657,7 +657,7 @@ NOEXPORT void print_cipher(CLI *c) { /* print negotiated cipher */
 NOEXPORT void transfer(CLI *c) {
     int timeout; /* s_poll_wait timeout in seconds */
     int pending; /* either processed on unprocessed TLS data */
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
     int has_pending=0, prev_has_pending;
 #endif
     int watchdog=0; /* a counter to detect an infinite loop */
@@ -705,7 +705,7 @@ NOEXPORT void transfer(CLI *c) {
 
         /****************************** wait for an event */
         pending=SSL_pending(c->ssl);
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
         /* only attempt to process SSL_has_pending() data once */
         prev_has_pending=has_pending;
         has_pending=SSL_has_pending(c->ssl);
@@ -1109,7 +1109,7 @@ NOEXPORT void transfer(CLI *c) {
             s_log(LOG_ERR,
                 "please report the problem to Michal.Trojnara@stunnel.org");
             stunnel_info(LOG_ERR);
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
             s_log(LOG_ERR, "protocol=%s, SSL_pending=%d, SSL_has_pending=%d",
                 SSL_get_version(c->ssl),
                 SSL_pending(c->ssl), SSL_has_pending(c->ssl));
diff --git a/src/ctx.c b/src/ctx.c
index 01119f3..b73fdcb 100644
--- a/src/ctx.c
+++ b/src/ctx.c
@@ -91,7 +91,7 @@ NOEXPORT void set_prompt(const char *);
 NOEXPORT int ui_retry();
 
 /* session tickets */
-#if OPENSSL_VERSION_NUMBER >= 0x10101000L
+#if OPENSSL_VERSION_NUMBER >= 0x10101000L && !defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT int generate_session_ticket_cb(SSL *, void *);
 NOEXPORT int decrypt_session_ticket_cb(SSL *, SSL_SESSION *,
     const unsigned char *, size_t, SSL_TICKET_STATUS, void *);
@@ -130,7 +130,7 @@ NOEXPORT void sslerror_log(unsigned long, const char *, int, char *);
 
 /**************************************** initialize section->ctx */
 
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 typedef long unsigned SSL_OPTIONS_TYPE;
 #else
 typedef long SSL_OPTIONS_TYPE;
@@ -138,7 +138,7 @@ typedef long SSL_OPTIONS_TYPE;
 
 int context_init(SERVICE_OPTIONS *section) { /* init TLS context */
     /* create TLS context */
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
     if(section->option.client)
         section->ctx=SSL_CTX_new(TLS_client_method());
     else /* server mode */
@@ -234,7 +234,7 @@ int context_init(SERVICE_OPTIONS *section) { /* init TLS context */
 #endif
 
     /* setup session tickets */
-#if OPENSSL_VERSION_NUMBER >= 0x10101000L
+#if OPENSSL_VERSION_NUMBER >= 0x10101000L && !defined(LIBRESSL_VERSION_NUMBER)
     SSL_CTX_set_session_ticket_cb(section->ctx, generate_session_ticket_cb,
         decrypt_session_ticket_cb, NULL);
 #endif /* OpenSSL 1.1.1 or later */
@@ -493,7 +493,7 @@ NOEXPORT int ecdh_init(SERVICE_OPTIONS *section) {
 /**************************************** initialize OpenSSL CONF */
 
 NOEXPORT int conf_init(SERVICE_OPTIONS *section) {
-#if OPENSSL_VERSION_NUMBER>=0x10002000L
+#if OPENSSL_VERSION_NUMBER>=0x10002000L && !defined(LIBRESSL_VERSION_NUMBER)
     SSL_CONF_CTX *cctx;
     NAME_LIST *curr;
     char *cmd, *param;
@@ -979,7 +979,7 @@ NOEXPORT int ui_retry() {
 
 /**************************************** session tickets */
 
-#if OPENSSL_VERSION_NUMBER >= 0x10101000L
+#if OPENSSL_VERSION_NUMBER >= 0x10101000L && !defined(LIBRESSL_VERSION_NUMBER)
 
 typedef struct {
     void *session_authenticated;
@@ -1470,7 +1470,7 @@ NOEXPORT void info_callback(const SSL *ssl, int where, int ret) {
 
     c=SSL_get_ex_data((SSL *)ssl, index_ssl_cli);
     if(c) {
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
         OSSL_HANDSHAKE_STATE state=SSL_get_state(ssl);
 #else
         int state=SSL_get_state((SSL *)ssl);
diff --git a/src/options.c b/src/options.c
index 670adbe..a10cecd 100644
--- a/src/options.c
+++ b/src/options.c
@@ -81,7 +81,7 @@ NOEXPORT char *sni_init(SERVICE_OPTIONS *);
 NOEXPORT void sni_free(SERVICE_OPTIONS *);
 #endif /* !defined(OPENSSL_NO_TLSEXT) */
 
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT int str_to_proto_version(const char *);
 #else /* OPENSSL_VERSION_NUMBER<0x10100000L */
 NOEXPORT char *tls_methods_set(SERVICE_OPTIONS *, const char *);
@@ -96,7 +96,7 @@ NOEXPORT PSK_KEYS *psk_dup(PSK_KEYS *);
 NOEXPORT void psk_free(PSK_KEYS *);
 #endif /* !defined(OPENSSL_NO_PSK) */
 
-#if OPENSSL_VERSION_NUMBER>=0x10000000L
+#if OPENSSL_VERSION_NUMBER>=0x10000000L && !defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT TICKET_KEY *key_read(char *, char *);
 NOEXPORT TICKET_KEY *key_dup(TICKET_KEY *);
 NOEXPORT void key_free(TICKET_KEY *);
@@ -3104,7 +3104,7 @@ NOEXPORT char *parse_service_option(CMD cmd, SERVICE_OPTIONS **section_ptr,
         break;
     }
 
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 
     /* sslVersion */
     switch(cmd) {
@@ -3273,7 +3273,7 @@ NOEXPORT char *parse_service_option(CMD cmd, SERVICE_OPTIONS **section_ptr,
     }
 #endif
 
-#if OPENSSL_VERSION_NUMBER>=0x10000000L
+#if OPENSSL_VERSION_NUMBER>=0x10000000L && !defined(LIBRESSL_VERSION_NUMBER)
 
     /* ticketKeySecret */
     switch(cmd) {
@@ -3755,7 +3755,7 @@ NOEXPORT void sni_free(SERVICE_OPTIONS *section) {
 
 /**************************************** modern TLS version handling */
 
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 
 NOEXPORT int str_to_proto_version(const char *name) {
     if(!strcasecmp(name, "all"))
@@ -4079,7 +4079,7 @@ NOEXPORT void psk_free(PSK_KEYS *head) {
 
 /**************************************** read ticket key */
 
-#if OPENSSL_VERSION_NUMBER>=0x10000000L
+#if OPENSSL_VERSION_NUMBER>=0x10000000L && !defined(LIBRESSL_VERSION_NUMBER)
 
 NOEXPORT TICKET_KEY *key_read(char *arg, char *option) {
     char *key_str;
diff --git a/src/prototypes.h b/src/prototypes.h
index ebd413c..edd4341 100644
--- a/src/prototypes.h
+++ b/src/prototypes.h
@@ -244,7 +244,7 @@ typedef struct service_options_struct {
 #if OPENSSL_VERSION_NUMBER>=0x009080dfL
     long unsigned ssl_options_clear;
 #endif /* OpenSSL 0.9.8m or later */
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
     int min_proto_version, max_proto_version;
 #else /* OPENSSL_VERSION_NUMBER<0x10100000L */
     SSL_METHOD *client_method, *server_method;
@@ -706,7 +706,7 @@ int getnameinfo(const struct sockaddr *, socklen_t,
 extern CLI *thread_head;
 #endif
 
-#if OPENSSL_VERSION_NUMBER<0x10100004L
+#if OPENSSL_VERSION_NUMBER<0x10100004L || defined(LIBRESSL_VERSION_NUMBER)
 
 #ifdef USE_OS_THREADS
 
@@ -755,7 +755,7 @@ typedef enum {
 
 extern CRYPTO_RWLOCK *stunnel_locks[STUNNEL_LOCKS];
 
-#if OPENSSL_VERSION_NUMBER<0x10100004L
+#if OPENSSL_VERSION_NUMBER<0x10100004L || defined(LIBRESSL_VERSION_NUMBER)
 /* Emulate the OpenSSL 1.1 locking API for older OpenSSL versions */
 CRYPTO_RWLOCK *CRYPTO_THREAD_lock_new(void);
 int CRYPTO_THREAD_read_lock(CRYPTO_RWLOCK *);
diff --git a/src/ssl.c b/src/ssl.c
index 60e31c1..10b0658 100644
--- a/src/ssl.c
+++ b/src/ssl.c
@@ -39,7 +39,7 @@
 #include "prototypes.h"
 
     /* global OpenSSL initialization: compression, engine, entropy */
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT int cb_dup_addr(CRYPTO_EX_DATA *to, const CRYPTO_EX_DATA *from,
     void *from_d, int idx, long argl, void *argp);
 #else
@@ -114,7 +114,7 @@ int DH_set0_pqg(DH *dh, BIGNUM *p, BIGNUM *q, BIGNUM *g) {
 #endif
 #endif
 
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT int cb_dup_addr(CRYPTO_EX_DATA *to, const CRYPTO_EX_DATA *from,
         void *from_d, int idx, long argl, void *argp) {
 #else
@@ -177,7 +177,7 @@ int ssl_configure(GLOBAL_OPTIONS *global) { /* configure global TLS settings */
 
 #ifndef OPENSSL_NO_COMP
 
-#if OPENSSL_VERSION_NUMBER<0x10100000L
+#if OPENSSL_VERSION_NUMBER<0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
 
 NOEXPORT int COMP_get_type(const COMP_METHOD *meth) {
     return meth->type;
diff --git a/src/sthreads.c b/src/sthreads.c
index dc2cd43..7a01f2e 100644
--- a/src/sthreads.c
+++ b/src/sthreads.c
@@ -102,14 +102,16 @@ unsigned long stunnel_thread_id(void) {
 
 #endif /* USE_WIN32 */
 
-#if OPENSSL_VERSION_NUMBER>=0x10000000L && OPENSSL_VERSION_NUMBER<0x10100004L
+#if (OPENSSL_VERSION_NUMBER>=0x10000000L && OPENSSL_VERSION_NUMBER<0x10100004L) || \
+    defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT void threadid_func(CRYPTO_THREADID *tid) {
     CRYPTO_THREADID_set_numeric(tid, stunnel_thread_id());
 }
 #endif
 
 void thread_id_init(void) {
-#if OPENSSL_VERSION_NUMBER>=0x10000000L && OPENSSL_VERSION_NUMBER<0x10100000L
+#if (OPENSSL_VERSION_NUMBER>=0x10000000L && OPENSSL_VERSION_NUMBER<0x10100000L) || \
+    defined(LIBRESSL_VERSION_NUMBER)
     CRYPTO_THREADID_set_callback(threadid_func);
 #endif
 #if OPENSSL_VERSION_NUMBER<0x10000000L || !defined(OPENSSL_NO_DEPRECATED)
@@ -120,7 +122,7 @@ void thread_id_init(void) {
 /**************************************** locking */
 
 /* we only need to initialize locking with OpenSSL older than 1.1.0 */
-#if OPENSSL_VERSION_NUMBER<0x10100004L
+#if OPENSSL_VERSION_NUMBER<0x10100004L || defined(LIBRESSL_VERSION_NUMBER)
 
 #ifdef USE_PTHREAD
 
@@ -229,7 +231,7 @@ NOEXPORT int s_atomic_add(int *val, int amount, CRYPTO_RWLOCK *lock) {
 
 CRYPTO_RWLOCK *stunnel_locks[STUNNEL_LOCKS];
 
-#if OPENSSL_VERSION_NUMBER<0x10100004L
+#if OPENSSL_VERSION_NUMBER<0x10100004L || defined(LIBRESSL_VERSION_NUMBER)
 
 #ifdef USE_OS_THREADS
 
@@ -339,7 +341,8 @@ int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock) {
 
 void locking_init(void) {
     size_t i;
-#if defined(USE_OS_THREADS) && OPENSSL_VERSION_NUMBER<0x10100004L
+#if defined(USE_OS_THREADS) && \
+    (OPENSSL_VERSION_NUMBER<0x10100004L || defined(LIBRESSL_VERSION_NUMBER))
     size_t num;
 
     /* initialize the OpenSSL static locking */
diff --git a/src/tls.c b/src/tls.c
index 6c92b96..5e60a95 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -41,7 +41,7 @@
 volatile int tls_initialized=0;
 
 NOEXPORT void tls_platform_init();
-#if OPENSSL_VERSION_NUMBER<0x10100000L
+#if OPENSSL_VERSION_NUMBER<0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT void free_function(void *);
 #endif
 
@@ -52,7 +52,7 @@ void tls_init() {
     tls_platform_init();
     tls_initialized=1;
     ui_tls=tls_alloc(NULL, NULL, "ui");
-#if OPENSSL_VERSION_NUMBER>=0x10100000L
+#if OPENSSL_VERSION_NUMBER>=0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
     CRYPTO_set_mem_functions(str_alloc_detached_debug,
         str_realloc_detached_debug, str_free_debug);
 #else
@@ -184,7 +184,7 @@ TLS_DATA *tls_get() {
 
 /**************************************** OpenSSL allocator hook */
 
-#if OPENSSL_VERSION_NUMBER<0x10100000L
+#if OPENSSL_VERSION_NUMBER<0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
 NOEXPORT void free_function(void *ptr) {
     /* CRYPTO_set_mem_ex_functions() needs a function rather than a macro */
     /* unfortunately, OpenSSL provides no file:line information here */
diff --git a/src/verify.c b/src/verify.c
index 1d1eccb..dfd9bff 100644
--- a/src/verify.c
+++ b/src/verify.c
@@ -346,7 +346,7 @@ NOEXPORT int cert_check_local(X509_STORE_CTX *callback_ctx) {
     cert=X509_STORE_CTX_get_current_cert(callback_ctx);
     subject=X509_get_subject_name(cert);
 
-#if OPENSSL_VERSION_NUMBER<0x10100006L
+#if OPENSSL_VERSION_NUMBER<0x10100006L || defined(LIBRESSL_VERSION_NUMBER)
 #define X509_STORE_CTX_get1_certs X509_STORE_get1_certs
 #endif
     /* modern API allows retrieving multiple matching certificates */