diff --git a/libs/libc/stream/CMakeLists.txt b/libs/libc/stream/CMakeLists.txt
index 4640f5e272..5bdcc60158 100644
--- a/libs/libc/stream/CMakeLists.txt
+++ b/libs/libc/stream/CMakeLists.txt
@@ -35,6 +35,7 @@ list(
   lib_nullinstream.c
   lib_nulloutstream.c
   lib_mtdoutstream.c
+  lib_mtdsostream.c
   lib_libnoflush.c
   lib_libsnoflush.c
   lib_syslogstream.c
diff --git a/libs/libc/stream/Make.defs b/libs/libc/stream/Make.defs
index d605efbb63..30c5f3e52e 100644
--- a/libs/libc/stream/Make.defs
+++ b/libs/libc/stream/Make.defs
@@ -30,6 +30,7 @@ CSRCS += lib_zeroinstream.c lib_nullinstream.c lib_nulloutstream.c
 CSRCS += lib_mtdoutstream.c lib_libnoflush.c lib_libsnoflush.c
 CSRCS += lib_syslogstream.c lib_syslograwstream.c lib_bufferedoutstream.c
 CSRCS += lib_hexdumpstream.c lib_base64outstream.c lib_fileoutstream.c
+CSRCS += lib_mtdsostream.c
 
 # The remaining sources files depend upon C streams