diff --git a/Kernel/filesys.c b/Kernel/filesys.c
index 6c9d4ac7ed..be24b711b3 100644
--- a/Kernel/filesys.c
+++ b/Kernel/filesys.c
@@ -261,7 +261,7 @@ inoptr srch_mt(register inoptr ino)
  * inodes.
  */
 
-inoptr i_open(uint16_t dev, uint16_t ino)
+inoptr i_open(register uint16_t dev, uint16_t ino)
 {
     register inoptr nindex;
     register inoptr j;
diff --git a/Kernel/syscall_exec16.c b/Kernel/syscall_exec16.c
index f5071bd982..dc7dc4b11b 100644
--- a/Kernel/syscall_exec16.c
+++ b/Kernel/syscall_exec16.c
@@ -9,8 +9,8 @@
 static void close_on_exec(void)
 {
 	/* Keep the mask separate to stop SDCC generating crap code */
-	uint16_t m = 1U << (UFTSIZE - 1);
-	int8_t j;
+	register uint16_t m = 1U << (UFTSIZE - 1);
+	register int_fast8_t j;
 
 	for (j = UFTSIZE - 1; j >= 0; --j) {
 		if (udata.u_cloexec & m)
@@ -34,7 +34,7 @@ char *envp[];
 /*
  *	See exec.h
  */
-static int header_ok(struct exec *pp)
+static int header_ok(register struct exec *pp)
 {
 	/* Executable ? */
 	if (pp->a_magic != EXEC_MAGIC)