diff --git a/host/src/routines/arithmatic/mult.s b/host/src/routines/arithmatic/mult.s
index f22f76f..fe064b6 100644
--- a/host/src/routines/arithmatic/mult.s
+++ b/host/src/routines/arithmatic/mult.s
@@ -11,8 +11,13 @@
 
         .include "arithmatic.inc"
 
-        LDA #$00
-        JMP start
+        LDA #$00 ;; A = value to return.
+
+        ;; 0 * 0 will never terminate so we need to fix this.
+        LDX VAL_A
+        BNE start
+        ;;  Now we have 0 * something. Instead of handeling [something = 0] we are more general and always return 0.
+        RTS ;; returning A = 0.
 loop:
         ASL VAL_B
 start:
diff --git a/host/src/routines/arithmatic/mult_test.s b/host/src/routines/arithmatic/mult_test.s
index 2095ef2..252a9a7 100644
--- a/host/src/routines/arithmatic/mult_test.s
+++ b/host/src/routines/arithmatic/mult_test.s
@@ -1,10 +1,34 @@
 ;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
 ;;Calculates $11 * $0E = $EE
 .scope mult_test
+        A_temp = $4043
+        B_temp = $4046
         .include "arithmatic.inc"
-        LDA #$0F
-        STA VAL_A
-        LDA #$07
-        STA VAL_B
-        JSR mult; A = $69 if it works as it should
+        .repeat $0F, i ;; $15 = floor(sqrt($255))
+        ;; now i * j_max = $FF --> j_max = $FF/i
+        .repeat $0F, j
+        INC $400D ;; print number of iterations on screen.
+        LDX #i
+        STX VAL_A
+        STX A_temp
+        LDY #j
+        STY VAL_B
+        STY B_temp
+        JSR mult; A = VAL_A * VAL_B, clobers X.
+
+        CMP #i*j
+        BEQ :+
+        jmp error
+        :
+        .endrepeat
+        .endrepeat
+        jmp end
+error:
+        ;; Error make screen read
+        ;; X * Y has the result in A that is wrong.
+        LDX #$02
+        STX $D020
+end:
+        LDX A_temp
+        LDY B_temp
 .endscope