diff --git a/os/hal/include/hal_flash.h b/os/hal/include/hal_flash.h
index af814bb4f..ba90a765e 100644
--- a/os/hal/include/hal_flash.h
+++ b/os/hal/include/hal_flash.h
@@ -103,7 +103,8 @@ typedef enum {
   FLASH_ERROR_PROGRAM = 3,      /* Program operation failed.                */
   FLASH_ERROR_ERASE = 4,        /* Erase operation failed.                  */
   FLASH_ERROR_VERIFY = 5,       /* Verify operation failed.                 */
-  FLASH_ERROR_HW_FAILURE = 6    /* Controller or communication error.       */
+  FLASH_ERROR_HW_FAILURE = 6,   /* Controller or communication error.       */
+  FLASH_ERROR_UNIMPLEMENTED = 7 /* Unimplemented functionality.             */
 } flash_error_t;
 
 /**
diff --git a/os/hal/ports/STM32/STM32F1xx/hal_efl_lld.c b/os/hal/ports/STM32/STM32F1xx/hal_efl_lld.c
index eab83cf89..3032085fa 100644
--- a/os/hal/ports/STM32/STM32F1xx/hal_efl_lld.c
+++ b/os/hal/ports/STM32/STM32F1xx/hal_efl_lld.c
@@ -334,7 +334,7 @@ flash_error_t efl_lld_program(void *instance, flash_offset_t offset,
 flash_error_t efl_lld_start_erase_all(void *instance) {
   (void) instance;
 
-  return FLASH_ERROR_HW_FAILURE;
+  return FLASH_ERROR_UNIMPLEMENTED;
 }
 
 /**