diff --git a/CMakeLists.txt b/CMakeLists.txt
index c08b90e..f558791 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,7 +25,7 @@ pico_sdk_init()
 
 # Add executable. Default name is the project name, version 0.1
 
-add_executable(sint-gauntlet sint-gauntlet.c )
+add_executable(sint-gauntlet sint-gauntlet.c vco.c )
 
 pico_set_program_name(sint-gauntlet "sint-gauntlet")
 pico_set_program_version(sint-gauntlet "0.1")