diff --git a/libsrc/cbm/c_chkin.s b/libsrc/cbm/c_chkin.s
index f687147ac..4565e6fb9 100644
--- a/libsrc/cbm/c_chkin.s
+++ b/libsrc/cbm/c_chkin.s
@@ -10,7 +10,8 @@
 _cbm_k_chkin:
 	tax
        	jsr    	CHKIN
+	ldx     #0              ; Clear high byte
 	bcs	@NotOk
-        lda     #0
+        txa
 @NotOk:	rts
 
diff --git a/libsrc/cbm/c_ckout.s b/libsrc/cbm/c_ckout.s
index 299254c03..faeee4b70 100644
--- a/libsrc/cbm/c_ckout.s
+++ b/libsrc/cbm/c_ckout.s
@@ -11,6 +11,7 @@
 _cbm_k_ckout:
 	tax
        	jsr    	CKOUT
+	ldx     #0              ; Clear high byte
 	bcs	@NotOk
-	lda     #0
+        txa
 @NotOk:	rts