diff --git a/keyboards/sirius/uni660/rev1/rules.mk b/keyboards/sirius/uni660/rev1/rules.mk
index e40e00c583..af1189024e 100644
--- a/keyboards/sirius/uni660/rev1/rules.mk
+++ b/keyboards/sirius/uni660/rev1/rules.mk
@@ -24,4 +24,4 @@ UNICODE_ENABLE = yes        # Unicode
 CUSTOM_MATRIX = yes
 
 # project specific files
-SRC += matrix.c
+SRC += matrix.c serial_uart.c
diff --git a/keyboards/sirius/uni660/rev2/rules.mk b/keyboards/sirius/uni660/rev2/rules.mk
index b6ac2d1c00..1f897b21f7 100644
--- a/keyboards/sirius/uni660/rev2/rules.mk
+++ b/keyboards/sirius/uni660/rev2/rules.mk
@@ -24,6 +24,6 @@ UNICODE_ENABLE = yes        # Unicode
 CUSTOM_MATRIX = yes
 
 # project specific files
-SRC += matrix.c
+SRC += matrix.c serial_uart.c
 
 DEFAULT_FOLDER = sirius/uni660/rev2/ansi