diff --git a/ChangeLog b/ChangeLog
index b46bb75c8..e647b12bf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2021-02-12 Frederik Seiffert <frederik@algoriddim.com>
+
+  * Headers/Foundation/NSNull.h: Add missing GS_EXPORT_CLASS.
+  * Tests/base/Functions/NSByteSwapping.m: Define M_PI if needed.
+  * configure:
+  * configure.ac: Add support for pthreadVC2 library variant and
+  tweak host OS check for Windows to be more specific.
+
 2021-02-05 Fred Kiefer <fredkiefer@gmx.de>
 
         * Tools/make_strings/StringsFile.m: Write the file in UTF8 format
diff --git a/Headers/Foundation/NSNull.h b/Headers/Foundation/NSNull.h
index b584d71c9..63d072861 100644
--- a/Headers/Foundation/NSNull.h
+++ b/Headers/Foundation/NSNull.h
@@ -37,6 +37,7 @@ extern "C" {
 /*
  * An object to use as a placeholder - in collections for instance.
  */
+GS_EXPORT_CLASS
 @interface	NSNull : NSObject <NSCoding, NSCopying>
 + (NSNull*) null;
 @end
diff --git a/Tests/base/Functions/NSByteSwapping.m b/Tests/base/Functions/NSByteSwapping.m
index c2759af77..6f61f3e07 100644
--- a/Tests/base/Functions/NSByteSwapping.m
+++ b/Tests/base/Functions/NSByteSwapping.m
@@ -1,6 +1,10 @@
 #import <Foundation/Foundation.h>
 #import "Testing.h"
 
+#ifndef M_PI
+#define M_PI 3.14159265358979323846264338327950288
+#endif
+
 int main()
 { 
   NSAutoreleasePool   *pool = [NSAutoreleasePool new];
diff --git a/configure b/configure
index ec693bc87..e04def347 100755
--- a/configure
+++ b/configure
@@ -6119,7 +6119,7 @@ if test "$gs_cv_objc_libdir" != "NONE"; then
 
   # add to path on Windows for config checks to find DLL at runtime
   case $host_os in
-    mingw*|windows*) PATH=$PATH:$gs_cv_objc_libdir;;
+    mingw*|windows) PATH=$PATH:$gs_cv_objc_libdir;;
   esac
 fi
 
@@ -7512,6 +7512,7 @@ ismingw=no
 checkinlibc=no
 case "$target_os" in
   mingw*)	ismingw=yes;;
+  windows) iswindows=yes;;
   nto*)		checkinlibc=yes;;
   qnx*)		checkinlibc=yes;;
   *android*)   checkinlibc=yes;;
@@ -7566,6 +7567,53 @@ fi
       LIBS="$LIBS -lpthreadGC2"
     fi
   fi
+  if test $iswindows = yes ; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join in -lpthreadVC2" >&5
+$as_echo_n "checking for pthread_join in -lpthreadVC2... " >&6; }
+if ${ac_cv_lib_pthreadVC2_pthread_join+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lpthreadVC2  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_pthreadVC2_pthread_join=yes
+else
+  ac_cv_lib_pthreadVC2_pthread_join=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_pthreadVC2_pthread_join" >&5
+$as_echo "$ac_cv_lib_pthreadVC2_pthread_join" >&6; }
+if test "x$ac_cv_lib_pthreadVC2_pthread_join" = xyes; then :
+  pthread_ok=yes
+else
+  pthread_ok=no
+fi
+
+    if test $pthread_ok = yes ; then
+      LIBS="$LIBS -lpthreadVC2"
+    fi
+  fi
   # Android and QNX have pthread in libc instead of libpthread
   if test $checkinlibc = yes ; then
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join in -lc" >&5
diff --git a/configure.ac b/configure.ac
index 834441ca7..aebf20ede 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1349,7 +1349,7 @@ if test "$gs_cv_objc_libdir" != "NONE"; then
 
   # add to path on Windows for config checks to find DLL at runtime
   case $host_os in
-    mingw*|windows*) PATH=$PATH:$gs_cv_objc_libdir;;
+    mingw*|windows) PATH=$PATH:$gs_cv_objc_libdir;;
   esac
 fi
 
@@ -1757,6 +1757,7 @@ ismingw=no
 checkinlibc=no
 case "$target_os" in
   mingw*)	ismingw=yes;;
+  windows) iswindows=yes;;
   nto*)		checkinlibc=yes;;
   qnx*)		checkinlibc=yes;;
   *android*)   checkinlibc=yes;;
@@ -1770,6 +1771,12 @@ else
       LIBS="$LIBS -lpthreadGC2"
     fi
   fi
+  if test $iswindows = yes ; then
+    AC_CHECK_LIB(pthreadVC2, pthread_join, pthread_ok=yes, pthread_ok=no)
+    if test $pthread_ok = yes ; then
+      LIBS="$LIBS -lpthreadVC2"
+    fi
+  fi
   # Android and QNX have pthread in libc instead of libpthread
   if test $checkinlibc = yes ; then
     AC_CHECK_LIB(c, pthread_join, pthread_ok=yes, pthread_ok=no)