diff --git a/i18npool/Library_i18nisolang1.mk b/i18npool/Library_i18nisolang1.mk
index 869c21aa637b..3864c6eac574 100644
--- a/i18npool/Library_i18nisolang1.mk
+++ b/i18npool/Library_i18nisolang1.mk
@@ -61,6 +61,11 @@ ifeq ($(ENABLE_LIBLANGTAG),YES)
 $(eval $(call gb_Library_add_defs,i18nisolang1,-DENABLE_LIBLANGTAG))
 $(eval $(call gb_Library_use_external,i18nisolang1,liblangtag))
 $(eval $(call gb_Library_use_external,i18nisolang1,libxml2))
+$(eval $(call gb_Library_use_system_win32_libs,i18nisolang1,\
+        $(if $(filter $(COM),MSC), \
+                kernel32 \
+        ) \
+))
 endif
 
 # vim: set noet sw=4 ts=4:
diff --git a/liblangtag/liblangtag-0.4.0-windows.patch b/liblangtag/liblangtag-0.4.0-windows.patch
index 30b3a0c2e0aa..1f2e6d8d5c9f 100644
--- a/liblangtag/liblangtag-0.4.0-windows.patch
+++ b/liblangtag/liblangtag-0.4.0-windows.patch
@@ -120,7 +120,7 @@
 +{
 +       lt_return_val_if_fail (v != NULL, 0);
 +
-+       return (int)InterlockedAdd((LONG*)v, 0);
++       return (int)InterlockedExchangeAdd((LONG*)v, 0);
 +}
 +
 +LT_INLINE_FUNC int
@@ -128,7 +128,7 @@
 +{
 +       lt_return_val_if_fail (v != NULL, 0);
 +
-+       return (int)InterlockedAdd((LONG*)v, 1);
++       return (int)InterlockedExchangeAdd((LONG*)v, 1) + 1;
 +}
 +
 +lt_bool_t
@@ -136,7 +136,7 @@
 +{
 +       lt_return_val_if_fail (v != NULL, FALSE);
 +
-+       return 1 == InterlockedAdd((LONG*)v, -1);
++       return 1 == InterlockedExchangeAdd((LONG*)v, -1) - 1;
 +}
 +
 +