diff --git a/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt b/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
index 9e4f1f2de..c118aea0a 100644
--- a/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
+++ b/codeOptimizers/src/prog8/optimizer/UnusedCodeRemover.kt
@@ -216,7 +216,7 @@ class UnusedCodeRemover(private val program: Program,
             val assign2 = stmtPairs[1] as? Assignment
             if (assign1 != null && assign2 != null) {
                 val cvalue1 = assign1.value.constValue(program)
-                if(cvalue1!=null && cvalue1.number==0.0 && assign2.isAugmentable) {
+                if(cvalue1!=null && cvalue1.number==0.0 && assign2.target.isSameAs(assign1.target, program) && assign2.isAugmentable) {
                     val value2 = assign2.value
                     val zero = VarDecl.defaultZero(value2.inferType(program).getOr(DataType.UNDEFINED), value2.position)
                     when(value2) {
diff --git a/compiler/test/TestOptimization.kt b/compiler/test/TestOptimization.kt
index e2cb09133..c4de14e25 100644
--- a/compiler/test/TestOptimization.kt
+++ b/compiler/test/TestOptimization.kt
@@ -15,6 +15,7 @@ import prog8.ast.base.Position
 import prog8.ast.expressions.*
 import prog8.ast.statements.*
 import prog8.compiler.BeforeAsmGenerationAstChanger
+import prog8.compiler.printProgram
 import prog8.compiler.target.C64Target
 import prog8.compilerinterface.*
 import prog8tests.helpers.*
@@ -527,4 +528,42 @@ class TestOptimization: FunSpec({
         stmts.filterIsInstance<VarDecl>().size shouldBe 3
         stmts.filterIsInstance<Assignment>().size shouldBe 5
     }
+
+    test("only substitue assignments with 0 after a =0 initializer if it is the same variable") {
+        val src="""
+        main {
+            sub start() {
+                uword @shared xx
+                xx = xx + 20    ; is same var so can be changed just fine into xx=20
+                uword @shared yy
+                xx = 20
+                yy = 0          ; is other var..
+                xx = xx+10      ; so this should not be changed into xx=10
+            }
+        }"""
+        val result = compileText(C64Target, optimize=true, src, writeAssembly=false).assertSuccess()
+        /*
+        expected result:
+        uword xx
+        xx = 20
+        uword yy
+        yy = 0
+        xx = 20
+        yy = 0
+        xx += 10
+         */
+        val stmts = result.program.entrypoint.statements
+        stmts.size shouldBe 7
+        stmts.filterIsInstance<VarDecl>().size shouldBe 2
+        stmts.filterIsInstance<Assignment>().size shouldBe 5
+        val assignXX1 = stmts[1] as Assignment
+        assignXX1.target.identifier!!.nameInSource shouldBe listOf("xx")
+        assignXX1.value shouldBe NumericLiteralValue(DataType.UBYTE, 20.0, Position.DUMMY)
+        val assignXX2 = stmts.last() as Assignment
+        assignXX2.target.identifier!!.nameInSource shouldBe listOf("xx")
+        val xxValue = assignXX2.value as BinaryExpression
+        xxValue.operator shouldBe "+"
+        xxValue.left shouldBe IdentifierReference(listOf("xx"), Position.DUMMY)
+        xxValue.right shouldBe NumericLiteralValue(DataType.UBYTE, 10.0, Position.DUMMY)
+    }
 })
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index de2e45cbb..a45d41ac4 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,6 +3,9 @@ TODO
 
 For next compiler release (7.4)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+BUG: amiga example doesn't clear the whole screen when compiled with optimizations (ok without opts)
+     same sort of problem in bobs example, and highresbitmap, and testgfx2
+
 ...
 
 
diff --git a/examples/test.p8 b/examples/test.p8
index 7a81d626d..da2cd9604 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,50 +4,30 @@ main {
 
     sub start() {
 
-        %asm {{
-
-        lda  $d020
-        ldy  $d021
-        sta  $d020
-        sty  $d021
-        lda  $d020
-        ldy  $d021
-        sta  $d020
-        sty  $d021
-
-
-        lda $d020
-        sta $d020
-        lda $d020
-        sta $d020
-        lda $d020
-        sta $d020
-        lda $d020
-        sta $d020
-        sta $d020
-        sta $d020
-        sta $d020
-        sta $d020
-        sta $d020
-        sta $d020
-
-        lda $c020
-        sta $c020
-        lda $c020
-        sta $c020
-        lda $c020
-        sta $c020
-        lda $c020
-        sta $c020
-        sta $c020
-        sta $c020
-        sta $c020
-        sta $c020
-        sta $c020
-
-        }}
+        repeat 100 {
+            random_rgb12()
+            txt.print_ubhex(target_red,false)
+            txt.print_ubhex(target_green,false)
+            txt.print_ubhex(target_blue,false)
+            txt.nl()
+        }
 
         repeat {
         }
     }
+
+        ubyte target_red
+        ubyte target_green
+        ubyte target_blue
+
+        sub random_rgb12() {
+            do {
+                uword rr = rndw()
+                target_red = msb(rr) & 15
+                target_green = lsb(rr)
+                target_blue = target_green & 15
+                target_green >>= 4
+            } until target_red+target_green+target_blue >= 12
+        }
+
 }