diff --git a/libs/freetdm/openzap.vcproj b/libs/freetdm/openzap.vcproj
index f9eb82b703..af00754f66 100644
--- a/libs/freetdm/openzap.vcproj
+++ b/libs/freetdm/openzap.vcproj
@@ -184,6 +184,10 @@
 				RelativePath=".\src\zap_io.c"
 				>
 			</File>
+			<File
+				RelativePath=".\src\zap_isdn.c"
+				>
+			</File>
 			<File
 				RelativePath=".\src\zap_skel.c"
 				>
@@ -304,6 +308,10 @@
 				RelativePath=".\src\include\zap_config.h"
 				>
 			</File>
+			<File
+				RelativePath=".\src\include\zap_isdn.h"
+				>
+			</File>
 			<File
 				RelativePath=".\src\include\zap_skel.h"
 				>