diff --git a/src/libsrc/longjmp.pla b/src/libsrc/longjmp.pla
index 99aa92e..d5afa3c 100644
--- a/src/libsrc/longjmp.pla
+++ b/src/libsrc/longjmp.pla
@@ -60,10 +60,11 @@ export asm throw(env, retval)
         DEC     DST+1
         LDX     TMPL
         TXS
-        LDY     TMPL
+        LDY     #$FE
 -       LDA     (DST),Y
         STA     $0100,Y
-        INY
+        DEY
+        CPY     TMPL
         BNE     -
         LDX     ESP
         LDA     SRC