diff --git a/Makefile b/Makefile
index 5271de7..0b4e654 100644
--- a/Makefile
+++ b/Makefile
@@ -101,7 +101,7 @@ strings_test: all
 	@strings $(TARGET_farmduino_k15_HEX).bin | grep -q ".H.genesisK15"
 	@strings $(TARGET_farmduino_k16_HEX).bin | grep -q ".I.genesisK16"
 	@strings $(TARGET_express_k10_HEX).bin | grep -q ".E.expressK10"
-	@strings $(TARGET_express_k11_HEX).bin | grep -q ".E.expressK11"
+	@strings $(TARGET_express_k11_HEX).bin | grep -q ".D.expressK11"
 
 force_clean: remove_temp
 	$(RM) -r $(BUILD_DIR) $(BIN_DIR)
diff --git a/src/Config.h b/src/Config.h
index 85b232f..802553c 100644
--- a/src/Config.h
+++ b/src/Config.h
@@ -9,7 +9,7 @@
 #ifndef CONFIG_H_
 #define CONFIG_H_
 
-  const char SOFTWARE_VERSION[] = "6.6.20\0";
+  const char SOFTWARE_VERSION[] = "6.6.21\0";
 
   const int LOGGING = 0;
 
@@ -294,7 +294,7 @@ enum MdlSpiEncoders
 #endif
 
 #if defined(FARMDUINO_EXP_V22) && !defined(SOFTWARE_VERSION_SUFFIX)
-#define SOFTWARE_VERSION_SUFFIX ".E.expressK11\0"
+#define SOFTWARE_VERSION_SUFFIX ".D.expressK11\0"
 #endif
 
 #ifndef FARMBOT_BOARD_ID