diff --git a/optiboot/bootloaders/optiboot/optiboot.c b/optiboot/bootloaders/optiboot/optiboot.c
index 9beab24..8a851af 100644
--- a/optiboot/bootloaders/optiboot/optiboot.c
+++ b/optiboot/bootloaders/optiboot/optiboot.c
@@ -528,9 +528,9 @@ int main(void) {
        * Send optiboot version as "SW version"
        * Note that the references to memory are optimized away.
        */
-      if (which == 0x82) {
+      if (which == STK_SW_MINOR) {
 	  putch(optiboot_version & 0xFF);
-      } else if (which == 0x81) {
+      } else if (which == STK_SW_MAJOR) {
 	  putch(optiboot_version >> 8);
       } else {
 	/*
diff --git a/optiboot/bootloaders/optiboot/stk500.h b/optiboot/bootloaders/optiboot/stk500.h
index c75908c..420706a 100644
--- a/optiboot/bootloaders/optiboot/stk500.h
+++ b/optiboot/bootloaders/optiboot/stk500.h
@@ -42,3 +42,5 @@
 #define STK_READ_OSCCAL     0x76  // 'v'
 #define STK_READ_FUSE_EXT   0x77  // 'w'
 #define STK_READ_OSCCAL_EXT 0x78  // 'x'
+#define STK_SW_MAJOR        0x81  // ' '
+#define STK_SW_MINOR        0x82  // ' '