diff --git a/ports/stm32/boards/stm32l476xe.ld b/ports/stm32/boards/stm32l476xe.ld
index 22c4466c66b1..31929517d77f 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 40d679ac39d7..59c5d90b69ac 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 88221170b420..b42087319964 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 5ae67d1ec2f2..2b633cf16b18 100644
--- a/ports/stm32/flashbdev.c
+++ b/ports/stm32/flashbdev.c
@@ -95,14 +95,15 @@ STATIC byte flash_cache_mem[0x4000] __attribute__((aligned(4))); // 16k
 
 #elif defined(STM32L475xx) || defined(STM32L476xx) || defined(STM32L496xx)
 
+// The STM32L475/6 doesn't have CCRAM, so we use the 32K SRAM2 for this, although
+// 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[]; // size determined by linker file
+extern uint8_t _ram_fs_cache_end[];
 
-// The STM32L475/6 doesn't have CCRAM, so we use the 32K SRAM2 for this.
-#define CACHE_MEM_START_ADDR (&_ram_fs_cache_start)       // End of SRAM2 RAM segment-2k
-#define FLASH_SECTOR_SIZE_MAX (_ram_fs_cache_block_size)  // 2k max
+#define CACHE_MEM_START_ADDR ((uintptr_t)&_ram_fs_cache_start[0])
+#define FLASH_SECTOR_SIZE_MAX (&_ram_fs_cache_end[0] - &_ram_fs_cache_start[0]) // 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)