diff --git a/src/app/i2cbench/Makefile.inc b/src/app/i2cbench/Makefile.inc
index d0337fc3ddb22f2478ebfec32d96cefac5ef195e..15ce127c21d4966f9f6c5b8d223033aa3380b025 100644
--- a/src/app/i2cbench/Makefile.inc
+++ b/src/app/i2cbench/Makefile.inc
@@ -1 +1,5 @@
 arch_drivers += ,i2c
+
+ifneq (${i2cbench_setos}, )
+	COMMON_FLAGS += -DI2CBENCH_SETOS=${i2cbench_setos}
+endif
diff --git a/src/app/i2cbench/main.cc b/src/app/i2cbench/main.cc
index a630c6d24e450af51841fca026ab7a51e3e8257b..3237f67e2a1176fa8ff0db9f9f53ccd778f27808 100644
--- a/src/app/i2cbench/main.cc
+++ b/src/app/i2cbench/main.cc
@@ -22,12 +22,16 @@
 #include "driver/mmsimple.h"
 #endif
 
+#ifndef I2CBENCH_SETOS
+#error must define I2CBENCH_SETOS
+#endif
+
 void loop(void)
 {
 #ifdef DRIVER_LM75
 	//kout.printf_float(lm75.getTemp());
 	//kout << endl;
-	lm75.setOS(64);
+	lm75.setOS(I2CBENCH_SETOS);
 #endif
 #ifdef DRIVER_AM2320
 	am2320.read();