diff --git a/libraries/Filter/AP_Filter_config.h b/libraries/Filter/AP_Filter_config.h
index d94dd9df1b..d89e7a0a62 100644
--- a/libraries/Filter/AP_Filter_config.h
+++ b/libraries/Filter/AP_Filter_config.h
@@ -2,14 +2,16 @@
 
 #include <AP_HAL/AP_HAL_Boards.h>
 
-#ifndef AP_FILTER_NUM_FILTERS
-#if BOARD_FLASH_SIZE > 1024
-#define AP_FILTER_NUM_FILTERS 8
-#else
-#define AP_FILTER_NUM_FILTERS 0
-#endif
+#ifndef AP_FILTER_ENABLED
+#define AP_FILTER_ENABLED BOARD_FLASH_SIZE > 1024
 #endif
 
-#ifndef AP_FILTER_ENABLED
-#define AP_FILTER_ENABLED AP_FILTER_NUM_FILTERS > 0
-#endif
+#if AP_FILTER_ENABLED
+ #ifndef AP_FILTER_NUM_FILTERS
+ #if BOARD_FLASH_SIZE > 1024
+  #define AP_FILTER_NUM_FILTERS 8
+ #else
+  #define AP_FILTER_NUM_FILTERS 4
+ #endif // BOARD_FLASH_SIZE
+ #endif // AP_FILTER_NUM_FILTERS
+#endif // AP_FILTER_ENABLED