diff --git a/reflowctl/reflowctl.ino b/reflowctl/reflowctl.ino
index 189d88a..dca7824 100644
--- a/reflowctl/reflowctl.ino
+++ b/reflowctl/reflowctl.ino
@@ -19,7 +19,7 @@
 __attribute__((__unused__)) static unsigned int time = 0; // profile seconds
 __attribute__((__unused__)) static unsigned int temperatur = 25; // actual oven temp
 __attribute__((__unused__)) static unsigned int last_temperatur = 25; // last oven temp
-__attribute__((__unused__)) static unsigned int actual_dt = 0; // actual difference from last to actual temperatur
+__attribute__((__unused__)) static int actual_dt = 0; // actual difference from last to actual temperatur
 
 
 // profile temperatures