diff --git a/CMakeLists.txt b/CMakeLists.txt
index bad2407..e391325 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -141,11 +141,11 @@ ENDIF(WIN32)
 FIND_PACKAGE(Boost CONFIG COMPONENTS ${BOOST_COMPONENTS})
 
 IF(NOT WIN32)
-    MESSAGE(STATUS "Configuring fc to build on Unix/Apple")
+  MESSAGE(STATUS "Configuring fc to build on Unix/Apple")
 
-    if(NOT APPLE)
-        SET(rt_library rt)
-    endif(NOT APPLE)
+  IF(NOT APPLE AND NOT "${CMAKE_SYSTEM_NAME}" STREQUAL "OpenBSD")
+    SET(rt_library rt )
+  ENDIF(NOT APPLE AND NOT "${CMAKE_SYSTEM_NAME}" STREQUAL "OpenBSD")
 ENDIF(NOT WIN32)
 
 IF($ENV{OPENSSL_ROOT_DIR})
diff --git a/include/fc/string.hpp b/include/fc/string.hpp
index 7fbe2e5..8f269f0 100644
--- a/include/fc/string.hpp
+++ b/include/fc/string.hpp
@@ -17,7 +17,7 @@ namespace fc
   std::string to_pretty_string( int64_t );
   inline std::string to_string( int32_t v ) { return to_string( int64_t(v) ); }
   inline std::string to_string( uint32_t v ){ return to_string( uint64_t(v) ); }
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
   inline std::string to_string( size_t s) { return to_string(uint64_t(s)); }
 #endif
 
diff --git a/include/fc/variant.hpp b/include/fc/variant.hpp
index f7ef613..66c422e 100644
--- a/include/fc/variant.hpp
+++ b/include/fc/variant.hpp
@@ -153,7 +153,7 @@ namespace fc
    void to_variant( const uint128_t& var, variant& vo, uint32_t max_depth = 1 );
    void from_variant( const variant& var, uint128_t& vo, uint32_t max_depth = 1 );
 
-   #ifdef __APPLE__
+   #if defined(__APPLE__) or defined(__OpenBSD__)
    void to_variant( size_t s, variant& v, uint32_t max_depth = 1 );
    #elif !defined(_WIN32)
    void to_variant( long long int s,          variant& v, uint32_t max_depth = 1 );
@@ -229,7 +229,7 @@ namespace fc
         variant( uint32_t val, uint32_t max_depth = 1 );
         variant( int32_t val, uint32_t max_depth = 1 );
         variant( uint64_t val, uint32_t max_depth = 1 );
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
         variant( size_t val, uint32_t max_depth = 1 );
 #endif
         variant( int64_t val, uint32_t max_depth = 1 );
@@ -632,7 +632,7 @@ namespace fc
 
    template<typename T>
    void to_variant( const safe<T>& s, variant& v, uint32_t max_depth ) {
-      to_variant( s.value, v, max_depth );
+      to_variant( static_cast<T>(s.value), v, max_depth );
    }
 
    template<typename T>
diff --git a/src/crypto/elliptic_common.cpp b/src/crypto/elliptic_common.cpp
index dd89c3a..8e4f802 100644
--- a/src/crypto/elliptic_common.cpp
+++ b/src/crypto/elliptic_common.cpp
@@ -7,8 +7,6 @@
 
 #ifdef _WIN32
 # include <malloc.h>
-#else
-# include <alloca.h>
 #endif
 
 /* stuff common to all ecc implementations */
@@ -231,12 +229,11 @@ namespace fc { namespace ecc {
 
     static std::string _to_base58( const extended_key_data& key )
     {
-        size_t buf_len = key.size() + 4;
-        char *buffer = (char*)alloca(buf_len);
+        char buffer[key.size() + 4]; // it's a small static array => allocate on stack
         memcpy( buffer, key.data(), key.size() );
-        fc::sha256 double_hash = fc::sha256::hash( fc::sha256::hash( (char*) key.data(), key.size() ));
+        fc::sha256 double_hash = fc::sha256::hash( fc::sha256::hash( (char*)key.data(), key.size() ));
         memcpy( buffer + key.size(), double_hash.data(), 4 );
-        return fc::to_base58( buffer, buf_len );
+        return fc::to_base58( buffer, sizeof(buffer) );
     }
 
     static void _parse_extended_data( unsigned char* buffer, std::string base58 )
diff --git a/src/crypto/elliptic_secp256k1.cpp b/src/crypto/elliptic_secp256k1.cpp
index b180d44..11969fc 100644
--- a/src/crypto/elliptic_secp256k1.cpp
+++ b/src/crypto/elliptic_secp256k1.cpp
@@ -14,8 +14,6 @@
 
 #if _WIN32
 # include <malloc.h>
-#else
-# include <alloca.h>
 #endif
 
 #include "_elliptic_impl_priv.hpp"
diff --git a/src/crypto/openssl.cpp b/src/crypto/openssl.cpp
index 3f8df03..e4c0e88 100644
--- a/src/crypto/openssl.cpp
+++ b/src/crypto/openssl.cpp
@@ -39,7 +39,11 @@ namespace  fc
 
        ~openssl_scope()
        {
+#if not defined(LIBRESSL_VERSION_NUMBER)
+          // No FIPS in LibreSSL.
+          // https://marc.info/?l=openbsd-misc&m=139819485423701&w=2
           FIPS_mode_set(0);
+#endif
           CONF_modules_unload(1);
           EVP_cleanup();
           CRYPTO_cleanup_all_ex_data();
diff --git a/src/network/tcp_socket.cpp b/src/network/tcp_socket.cpp
index 0012ba6..1152496 100644
--- a/src/network/tcp_socket.cpp
+++ b/src/network/tcp_socket.cpp
@@ -11,6 +11,13 @@
 # include <mstcpip.h>
 #endif
 
+#if defined __OpenBSD__
+# include <sys/types.h>
+# include <sys/sysctl.h>
+# include <netinet/tcp_timer.h>
+# include <netinet/tcp_var.h>
+#endif
+
 namespace fc {
 
   namespace detail
@@ -186,16 +193,37 @@ namespace fc {
       if (setsockopt(my->_sock.native_handle(), IPPROTO_TCP,
       #if defined( __APPLE__ )
                      TCP_KEEPALIVE,
+       #elif defined( __OpenBSD__ )
+                     SO_KEEPALIVE,
        #else
                      TCP_KEEPIDLE, 
        #endif
                      (char*)&timeout_sec, sizeof(timeout_sec)) < 0)
         wlog("Error setting TCP keepalive idle time");
-# if !defined(__APPLE__) || defined(TCP_KEEPINTVL) // TCP_KEEPINTVL not defined before 10.9
+# if defined(__OpenBSD__)
+        int name[4];
+        name[0] = CTL_NET;
+        name[1] = PF_INET;
+        name[2] = IPPROTO_TCP;
+
+        int value;
+        size_t sz;
+
+        // get tics per second
+        name[3] = TCPCTL_SLOWHZ;
+        if (sysctl(name, 4, &value, &sz, NULL, 0) == -1)
+          wlog("Error setting TCP keepalive interval");
+
+        // set interval
+        value *= timeout_sec;
+        name[3] = TCPCTL_KEEPINTVL;
+        if (sysctl(name, 4, NULL, NULL, &value, sizeof(value)) == -1)
+          wlog("Error setting TCP keepalive interval");
+# elif !defined(__APPLE__) || defined(TCP_KEEPINTVL) // TCP_KEEPINTVL not defined before 10.9
       if (setsockopt(my->_sock.native_handle(), IPPROTO_TCP, TCP_KEEPINTVL,
                      (char*)&timeout_sec, sizeof(timeout_sec)) < 0)
         wlog("Error setting TCP keepalive interval");
-# endif // !__APPLE__ || TCP_KEEPINTVL
+# endif // (__OpenBSD__) or (!__APPLE__ || TCP_KEEPINTVL)
 #endif // !WIN32
     }
     else
diff --git a/src/stacktrace.cpp b/src/stacktrace.cpp
index 126691f..910b48f 100644
--- a/src/stacktrace.cpp
+++ b/src/stacktrace.cpp
@@ -8,6 +8,9 @@
 #if BOOST_VERSION / 100 >= 1065 && !defined(__APPLE__)
 #include <signal.h>
 #include <fc/log/logger.hpp>
+#if defined(__OpenBSD__)
+    #define BOOST_STACKTRACE_GNU_SOURCE_NOT_REQUIRED
+#endif
 #include <boost/stacktrace.hpp>
 
 namespace fc
diff --git a/src/variant.cpp b/src/variant.cpp
index 7a527e9..eaa12d3 100644
--- a/src/variant.cpp
+++ b/src/variant.cpp
@@ -11,7 +11,7 @@
 #include <fc/reflect/variant.hpp>
 #include <algorithm>
 
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
 #include <boost/multiprecision/integer.hpp>
 #endif
 
@@ -79,7 +79,7 @@ variant::variant( uint64_t val, uint32_t max_depth )
    set_variant_type( this, uint64_type );
 }
 
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
 variant::variant( size_t val, uint32_t max_depth )
 {
    *reinterpret_cast<uint64_t*>(this)  = val;
@@ -679,7 +679,7 @@ void from_variant( const variant& var, std::vector<char>& vo, uint32_t max_depth
 
 void to_variant( const uint128_t& var, variant& vo, uint32_t max_depth )
 {
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
    boost::multiprecision::uint128_t helper = uint128_hi64( var );
    helper <<= 64;
    helper += uint128_lo64( var );
@@ -691,7 +691,7 @@ void to_variant( const uint128_t& var, variant& vo, uint32_t max_depth )
 
 void from_variant( const variant& var, uint128_t& vo, uint32_t max_depth )
 {
-#ifdef __APPLE__
+#if defined(__APPLE__) or defined(__OpenBSD__)
    boost::multiprecision::uint128_t helper = boost::lexical_cast<boost::multiprecision::uint128_t>( var.as_string() );
    vo = static_cast<uint64_t>( helper >> 64 );
    vo <<= 64;
@@ -701,7 +701,9 @@ void from_variant( const variant& var, uint128_t& vo, uint32_t max_depth )
 #endif
 }
 
-#ifdef __APPLE__
+#if defined(__APPLE__)
+#elif defined(__OpenBSD__)
+   void to_variant( size_t s, variant& v, uint32_t max_depth ) { v = variant( int64_t(s) ); }
 #elif !defined(_WIN32)
    void to_variant( long long int s, variant& v, uint32_t max_depth ) { v = variant( int64_t(s) ); }
    void to_variant( unsigned long long int s, variant& v, uint32_t max_depth ) { v = variant( uint64_t(s)); }