diff --git a/Firmware/temperature.cpp b/Firmware/temperature.cpp
index 5a365d88..cf3f9364 100755
--- a/Firmware/temperature.cpp
+++ b/Firmware/temperature.cpp
@@ -2387,8 +2387,8 @@ static void setup()
 
 static bool calibrated()
 {
-    if(!(data.P >= 0)) return false;
-    if(!(data.C >= 0)) return false;
+    if(!(data.P > 0)) return false;
+    if(!(data.C > 0)) return false;
     if(!(data.Ta_corr != NAN)) return false;
     for(uint8_t i = 0; i != TEMP_MODEL_R_SIZE; ++i) {
         if(!(temp_model::data.R[i] >= 0))