diff --git a/keyboards/bfo9000/serial.c b/keyboards/bfo9000/serial.c
index 4936e4249..fea57b651 100644
--- a/keyboards/bfo9000/serial.c
+++ b/keyboards/bfo9000/serial.c
@@ -12,7 +12,7 @@
 #include <stdbool.h>
 #include "serial.h"
 
-#ifdef USE_SERIAL
+#ifndef USE_I2C
 
 // Serial pulse period in microseconds. Its probably a bad idea to lower this
 // value.
diff --git a/keyboards/deltasplit75/serial.c b/keyboards/deltasplit75/serial.c
index 6faed09ce..74bcbb6bf 100644
--- a/keyboards/deltasplit75/serial.c
+++ b/keyboards/deltasplit75/serial.c
@@ -12,7 +12,7 @@
 #include <stdbool.h>
 #include "serial.h"
 
-#ifdef USE_SERIAL
+#ifndef USE_I2C
 
 // Serial pulse period in microseconds. Its probably a bad idea to lower this
 // value.
diff --git a/keyboards/minidox/serial.c b/keyboards/minidox/serial.c
index 6faed09ce..74bcbb6bf 100644
--- a/keyboards/minidox/serial.c
+++ b/keyboards/minidox/serial.c
@@ -12,7 +12,7 @@
 #include <stdbool.h>
 #include "serial.h"
 
-#ifdef USE_SERIAL
+#ifndef USE_I2C
 
 // Serial pulse period in microseconds. Its probably a bad idea to lower this
 // value.
diff --git a/keyboards/viterbi/serial.c b/keyboards/viterbi/serial.c
index 6faed09ce..74bcbb6bf 100644
--- a/keyboards/viterbi/serial.c
+++ b/keyboards/viterbi/serial.c
@@ -12,7 +12,7 @@
 #include <stdbool.h>
 #include "serial.h"
 
-#ifdef USE_SERIAL
+#ifndef USE_I2C
 
 // Serial pulse period in microseconds. Its probably a bad idea to lower this
 // value.