diff --git a/reflowctl/reflowctl.ino b/reflowctl/reflowctl.ino
index 8d593d4..33bcf4e 100644
--- a/reflowctl/reflowctl.ino
+++ b/reflowctl/reflowctl.ino
@@ -125,21 +125,21 @@ static void print_debug() {
   Serial.println(error_condition);
 }
 
-boolean check_max_duration() {
+static boolean check_max_duration() {
   if (time > time_max) {
     error_condition |= E_TIME_MAX;
     return false;
   }
 }
 
-boolean check_Tl_duration() {
+static boolean check_Tl_duration() {
   if (time - Tl_time_start > Tp_duration) {
     error_condition |= E_TL_TOO_LONG;
     return false;
   }
 }
 
-boolean check_Tp_duration() {
+static boolean check_Tp_duration() {
   if (time - Tp_time_start > Tp_duration) {
     error_condition |= E_TP_TOO_LONG;
     return false;
@@ -197,7 +197,7 @@ static void set_end_state() {
 }
 
 
-void set_error_state() {
+static void set_error_state() {
   if (state != ERROR_STATE) {
     Serial.println("Changed state to ERROR_STATE");
     set_temp(0, 0, 0, 0);