diff --git a/ports/stm32/boards/stm32l476xe.ld b/ports/stm32/boards/stm32l476xe.ld
index 22c4466c6..31929517d 100644
--- a/ports/stm32/boards/stm32l476xe.ld
+++ b/ports/stm32/boards/stm32l476xe.ld
@@ -25,7 +25,7 @@ _estack = ORIGIN(RAM) + LENGTH(RAM);
 
 /* RAM extents for the garbage collector */
 _ram_fs_cache_start = ORIGIN(FS_CACHE);
-_ram_fs_cache_block_size = LENGTH(FS_CACHE);
+_ram_fs_cache_end = ORIGIN(FS_CACHE) + LENGTH(FS_CACHE);
 _ram_start = ORIGIN(RAM);
 _ram_end = ORIGIN(RAM) + LENGTH(RAM);
 _heap_start = _ebss; /* heap starts just after statically allocated memory */
diff --git a/ports/stm32/boards/stm32l476xg.ld b/ports/stm32/boards/stm32l476xg.ld
index 40d679ac3..59c5d90b6 100644
--- a/ports/stm32/boards/stm32l476xg.ld
+++ b/ports/stm32/boards/stm32l476xg.ld
@@ -25,7 +25,7 @@ _estack = ORIGIN(RAM) + LENGTH(RAM);
 
 /* RAM extents for the garbage collector */
 _ram_fs_cache_start = ORIGIN(FS_CACHE);
-_ram_fs_cache_block_size = LENGTH(FS_CACHE);
+_ram_fs_cache_end = ORIGIN(FS_CACHE) + LENGTH(FS_CACHE);
 _ram_start = ORIGIN(RAM);
 _ram_end = ORIGIN(RAM) + LENGTH(RAM);
 _heap_start = _ebss; /* heap starts just after statically allocated memory */
diff --git a/ports/stm32/boards/stm32l496xg.ld b/ports/stm32/boards/stm32l496xg.ld
index 88221170b..b42087319 100644
--- a/ports/stm32/boards/stm32l496xg.ld
+++ b/ports/stm32/boards/stm32l496xg.ld
@@ -25,7 +25,7 @@ _estack = ORIGIN(RAM) + LENGTH(RAM) + LENGTH(SRAM2);
 
 /* RAM extents for the garbage collector */
 _ram_fs_cache_start = ORIGIN(FS_CACHE);
-_ram_fs_cache_block_size = LENGTH(FS_CACHE);
+_ram_fs_cache_end = ORIGIN(FS_CACHE) + LENGTH(FS_CACHE);
 _ram_start = ORIGIN(RAM);
 _ram_end = ORIGIN(RAM) + LENGTH(RAM) + LENGTH(SRAM2);
 _heap_start = _ebss; /* heap starts just after statically allocated memory */
diff --git a/ports/stm32/flashbdev.c b/ports/stm32/flashbdev.c
index a36e3bcf7..406157029 100644
--- a/ports/stm32/flashbdev.c
+++ b/ports/stm32/flashbdev.c
@@ -99,11 +99,11 @@ STATIC byte flash_cache_mem[0x4000] __attribute__((aligned(4))); // 16k
 // actual location and size is defined by the linker script.
 extern uint8_t _flash_fs_start;
 extern uint8_t _flash_fs_end;
-extern uint32_t _ram_fs_cache_start[2048 / 4];
-extern uint32_t _ram_fs_cache_block_size;
+extern uint8_t _ram_fs_cache_start[0];      // size determined by linker file
+extern uint8_t _ram_fs_cache_end[0];
 
 #define CACHE_MEM_START_ADDR (&_ram_fs_cache_start)
-#define FLASH_SECTOR_SIZE_MAX ((uint32_t)(&_ram_fs_cache_block_size))   // 2k max
+#define FLASH_SECTOR_SIZE_MAX (_ram_fs_cache_end - _ram_fs_cache_start)   // 2k max
 #define FLASH_MEM_SEG1_START_ADDR ((long)&_flash_fs_start)
 #define FLASH_MEM_SEG1_NUM_BLOCKS ((&_flash_fs_end - &_flash_fs_start) / 512)