Index: firmware/App/Modes/ModeHeatDisinfect.c
===================================================================
diff -u -rf5dc98b3d5fcd39e3ab502fbe81110e188ce0ec5 -r33d5acc68ffe045546a4fa9a7d381950619ea45d
--- firmware/App/Modes/ModeHeatDisinfect.c	(.../ModeHeatDisinfect.c)	(revision f5dc98b3d5fcd39e3ab502fbe81110e188ce0ec5)
+++ firmware/App/Modes/ModeHeatDisinfect.c	(.../ModeHeatDisinfect.c)	(revision 33d5acc68ffe045546a4fa9a7d381950619ea45d)
@@ -15,6 +15,8 @@
 *
 ***************************************************************************/
 
+#include <math.h>   // For fabs
+
 #include "ConcentratePumps.h"
 #include "ConductivitySensors.h"
 #include "DrainPump.h"