diff --git a/libs/spandsp/src/libspandsp.2008.vcproj b/libs/spandsp/src/libspandsp.2008.vcproj
index 6f57c7801e..027a6fc664 100644
--- a/libs/spandsp/src/libspandsp.2008.vcproj
+++ b/libs/spandsp/src/libspandsp.2008.vcproj
@@ -226,6 +226,7 @@
 <File RelativePath="t38_terminal.c"></File>
 <File RelativePath="testcpuid.c"></File>
 <File RelativePath="time_scale.c"></File>
+<File RelativePath="timezone.c"></File>
 <File RelativePath="tone_detect.c"></File>
 <File RelativePath="tone_generate.c"></File>
 <File RelativePath="v17rx.c"></File>
@@ -294,6 +295,8 @@
 <File RelativePath="spandsp/swept_tone.h"></File>
 <File RelativePath="spandsp/t4_rx.h"></File>
 <File RelativePath="spandsp/t4_tx.h"></File>
+<File RelativePath="spandsp/t4_t6_decode.h"></File>
+<File RelativePath="spandsp/t4_t6_encode.h"></File>
 <File RelativePath="spandsp/t30.h"></File>
 <File RelativePath="spandsp/t30_api.h"></File>
 <File RelativePath="spandsp/t30_fcf.h"></File>
diff --git a/libs/spandsp/src/msvc/spandsp.h b/libs/spandsp/src/msvc/spandsp.h
index 4e06660bdf..deb146884e 100644
--- a/libs/spandsp/src/msvc/spandsp.h
+++ b/libs/spandsp/src/msvc/spandsp.h
@@ -101,6 +101,8 @@
 #include <spandsp/v42bis.h>
 #include <spandsp/t4_rx.h>
 #include <spandsp/t4_tx.h>
+#include <spandsp/t4_t6_decode.h>
+#include <spandsp/t4_t6_encode.h>
 #include <spandsp/t30.h>
 #include <spandsp/t30_api.h>
 #include <spandsp/t30_fcf.h>