diff --git a/external/unbound/CMakeLists.txt b/external/unbound/CMakeLists.txt
index 63ce2d22..4edb5123 100644
--- a/external/unbound/CMakeLists.txt
+++ b/external/unbound/CMakeLists.txt
@@ -31,7 +31,7 @@ cmake_minimum_required(VERSION 2.8.7)
 project(unbound C)
 
 if (APPLE)
-  if (not OpenSSL_DIR)
+  if (NOT OpenSSL_DIR)
       EXECUTE_PROCESS(COMMAND brew --prefix openssl
         OUTPUT_VARIABLE OPENSSL_ROOT_DIR
         OUTPUT_STRIP_TRAILING_WHITESPACE)
@@ -168,6 +168,11 @@ elseif (WIN32)
     compat/getentropy_win.c)
 endif ()
 
+if (NOT HAVE_ISBLANK)
+  list(APPEND compat_src
+    compat/isblank.c)
+endif ()
+
 if (NOT HAVE_GETADDRINFO)
   list(APPEND compat_src
     compat/fake-rfc2553.c)
diff --git a/external/unbound/configure_checks.cmake b/external/unbound/configure_checks.cmake
index 84c02ac9..edb64c78 100644
--- a/external/unbound/configure_checks.cmake
+++ b/external/unbound/configure_checks.cmake
@@ -49,6 +49,7 @@ if (WIN32)
     ws2_32)
 endif ()
 
+check_function_exists(_beginthreadex HAVE__BEGINTHREADEX)
 check_function_exists(arc4random HAVE_ARC4RANDOM)
 check_function_exists(arc4random_uniform HAVE_ARC4RANDOM_UNIFORM)
 check_function_exists(chown HAVE_CHOWN)
@@ -60,12 +61,14 @@ check_function_exists(endservent HAVE_ENDSERVENT)
 check_function_exists(fnctl HAVE_FNCTL)
 check_function_exists(fork HAVE_FORK)
 check_function_exists(fseeko HAVE_FSEEKO)
+check_function_exists(fsync HAVE_FSYNC)
 check_function_exists(getauxval HAVE_GETAUXVAL)
 check_function_exists(getentropy HAVE_GETENTROPY)
 check_function_exists(getpwnam HAVE_GETPWNAM)
 check_function_exists(getrlimit HAVE_GETRLIMIT)
 check_function_exists(glob HAVE_GLOB)
 check_function_exists(gmtime_r HAVE_GMTIME_R)
+check_function_exists(fcntl HAVE_FCNTL)
 check_function_exists(inet_aton HAVE_INET_ATON)
 check_function_exists(inet_ntop HAVE_INET_NTOP)
 check_function_exists(inet_pton HAVE_INET_PTON)