diff --git a/Firmware/Board/v3/Inc/main.h b/Firmware/Board/v3/Inc/main.h
index 02aae9cb..50256101 100644
--- a/Firmware/Board/v3/Inc/main.h
+++ b/Firmware/Board/v3/Inc/main.h
@@ -167,10 +167,12 @@
 #define CURRENT_MEAS_PERIOD ((float)(2*TIM_1_8_PERIOD_CLOCKS)/(float)TIM_1_8_CLOCK_HZ)
 #define CURRENT_MEAS_HZ (TIM_1_8_CLOCK_HZ/(2*TIM_1_8_PERIOD_CLOCKS))
 
-#ifdef HW_VERSION_HIGH_VOLTAGE
+#if HW_VERSION_VOLTAGE == 48
 #define VBUS_S_DIVIDER_RATIO 19.0f
-#else
+#elif HW_VERSION_VOLTAGE == 24
 #define VBUS_S_DIVIDER_RATIO 11.0f
+#else
+#error "unknown board voltage"
 #endif
 
 /* USER CODE END Private defines */
diff --git a/Firmware/Tupfile.lua b/Firmware/Tupfile.lua
index 2301c773..114a3c8c 100644
--- a/Firmware/Tupfile.lua
+++ b/Firmware/Tupfile.lua
@@ -6,23 +6,23 @@ boardversion = tup.getconfig("BOARD_VERSION")
 if boardversion == "v3.1" then
     boarddir = 'Board/v3' -- currently all platform code is in the same v3.3 directory
     FLAGS += "-DHW_VERSION_MAJOR=3 -DHW_VERSION_MINOR=1"
-    FLAGS += "-DHW_VERSION_HIGH_VOLTAGE=false"
+    FLAGS += "-DHW_VERSION_VOLTAGE=24"
 elseif boardversion == "v3.2" then
     boarddir = 'Board/v3'
     FLAGS += "-DHW_VERSION_MAJOR=3 -DHW_VERSION_MINOR=2"
-    FLAGS += "-DHW_VERSION_HIGH_VOLTAGE=false"
+    FLAGS += "-DHW_VERSION_VOLTAGE=24"
 elseif boardversion == "v3.3" then
     boarddir = 'Board/v3'
     FLAGS += "-DHW_VERSION_MAJOR=3 -DHW_VERSION_MINOR=3"
-    FLAGS += "-DHW_VERSION_HIGH_VOLTAGE=false"
+    FLAGS += "-DHW_VERSION_VOLTAGE=24"
 elseif boardversion == "v3.4-24V" then
     boarddir = 'Board/v3'
     FLAGS += "-DHW_VERSION_MAJOR=3 -DHW_VERSION_MINOR=4"
-    FLAGS += "-DHW_VERSION_HIGH_VOLTAGE=false"
+    FLAGS += "-DHW_VERSION_VOLTAGE=24"
 elseif boardversion == "v3.4-48V" then
     boarddir = 'Board/v3'
     FLAGS += "-DHW_VERSION_MAJOR=3 -DHW_VERSION_MINOR=4"
-    FLAGS += "-DHW_VERSION_HIGH_VOLTAGE=true"
+    FLAGS += "-DHW_VERSION_VOLTAGE=48"
 elseif boardversion == "" then
     error("board version not specified - take a look at tup.config.default")
 else