diff --git a/visualc/vngspice.vcxproj b/visualc/vngspice.vcxproj
index 157b44b85..455987b98 100644
--- a/visualc/vngspice.vcxproj
+++ b/visualc/vngspice.vcxproj
@@ -1678,6 +1678,7 @@
     <ClCompile Include="..\src\spicelib\analysis\ninteg.c" />
     <ClCompile Include="..\src\spicelib\analysis\noisean.c" />
     <ClCompile Include="..\src\spicelib\analysis\nsetparm.c" />
+    <ClCompile Include="..\src\spicelib\analysis\optran.c" />
     <ClCompile Include="..\src\spicelib\analysis\pssaskq.c" />
     <ClCompile Include="..\src\spicelib\analysis\pssinit.c" />
     <ClCompile Include="..\src\spicelib\analysis\psssetp.c" />