diff --git a/RepositoryExternal.mk b/RepositoryExternal.mk
index 11896cd801d8..86212220f7ef 100644
--- a/RepositoryExternal.mk
+++ b/RepositoryExternal.mk
@@ -901,6 +901,28 @@ endef
 endif # SYSTEM_CURL
 
 
+ifeq ($(SYSTEM_MOZILLA_HEADERS),YES)
+
+define gb_LinkTarget__use_mozilla_headers
+$(eval $(call gb_LinkTarget_set_include,$(1),\
+	$$(INCLUDE) \
+	$(MOZILLA_HEADERS_CFLAGS)
+))
+endef
+
+else #!SYSTEM_MOZILLA_HEADERS
+
+define gb_LinkTarget__use_mozilla_headers
+$(eval $(call gb_LinkTarget_set_include,$(1),\
+	$$(INCLUDE) \
+	-I$(OUTDIR)/inc/npsdk \
+))
+endef
+
+endif #SYSTEM_MOZILLA_HEADERS
+#TODO np_sdk $(eval $(call gb_LinkTarget_add_external_headers,$(1),np_sdk))
+
+
 # MacOSX-only frameworks ############################################
 # (in alphabetical order)
 
diff --git a/extensions/Library_npsoplugin.mk b/extensions/Library_npsoplugin.mk
index bf5f67e2de33..954ba8655c92 100644
--- a/extensions/Library_npsoplugin.mk
+++ b/extensions/Library_npsoplugin.mk
@@ -30,17 +30,7 @@
 
 $(eval $(call gb_Library_Library,npsoplugin))
 
-ifeq ($(SYSTEM_MOZILLA_HEADERS),YES)
-$(eval $(call gb_Library_set_include,npsoplugin,\
-	$$(INCLUDE) \
-	$(MOZILLA_HEADERS_CFLAGS)
-))
-else
-$(eval $(call gb_Library_set_include,npsoplugin,\
-	-I$(OUTDIR)/inc/npsdk \
-	$$(INCLUDE) \
-))
-endif
+$(eval $(call gb_Library_use_external,npsoplugin,mozilla_headers))
 
 ifeq ($(GUI),UNX)