diff --git a/compiler/src/prog8/ast/AstChecker.kt b/compiler/src/prog8/ast/AstChecker.kt
index 25d977220..3a97696b3 100644
--- a/compiler/src/prog8/ast/AstChecker.kt
+++ b/compiler/src/prog8/ast/AstChecker.kt
@@ -492,7 +492,7 @@ private class AstChecker(private val namespace: INameScope,
             checkResult.add(SyntaxError("floating point used, but that is not enabled via options", decl.position))
         }
 
-        // ARRAY without size specifier MUST have an initializer value
+        // ARRAY without size specifier MUST have an iterable initializer value
         if(decl.isUnsizedArray) {
             if(decl.type==VarDeclType.MEMORY)
                 checkResult.add(SyntaxError("memory mapped array must have a size specification", decl.position))
@@ -500,6 +500,12 @@ private class AstChecker(private val namespace: INameScope,
                 checkResult.add(SyntaxError("array variable is missing a size specification or an initialization value", decl.position))
                 return decl
             }
+            if(decl.value is LiteralValue && !(decl.value as LiteralValue).isArray) {
+                checkResult.add(SyntaxError("unsized array declaration cannot use a single literal initialization value", decl.position))
+                return decl
+            }
+            if(decl.value is RangeExpr)
+                throw FatalAstException("range expressions in vardecls should have been converted into array values during constFolding  $decl")
         }
 
         when(decl.type) {
diff --git a/compiler/src/prog8/optimizing/ConstantFolding.kt b/compiler/src/prog8/optimizing/ConstantFolding.kt
index db02631fd..5eeccd9eb 100644
--- a/compiler/src/prog8/optimizing/ConstantFolding.kt
+++ b/compiler/src/prog8/optimizing/ConstantFolding.kt
@@ -45,6 +45,24 @@ class ConstantFolding(private val namespace: INameScope, private val heap: HeapV
                     }
                 }
                 DataType.ARRAY_UB, DataType.ARRAY_B, DataType.ARRAY_UW, DataType.ARRAY_W -> {
+                    val rangeExpr = decl.value as? RangeExpr
+                    if(rangeExpr!=null) {
+                        // convert the initializer range expression to an actual array
+                        val constRange = rangeExpr.toConstantIntegerRange(heap)
+                        if(constRange!=null) {
+                            val eltType = rangeExpr.resultingDatatype(namespace, heap)!!
+                            if(eltType in ByteDatatypes) {
+                                decl.value = LiteralValue(decl.datatype,
+                                        arrayvalue = constRange.map { LiteralValue(eltType, bytevalue=it.toShort(), position = decl.value!!.position ) }
+                                                .toTypedArray(), position=decl.value!!.position)
+                            } else {
+                                decl.value = LiteralValue(decl.datatype,
+                                        arrayvalue = constRange.map { LiteralValue(eltType, wordvalue= it, position = decl.value!!.position ) }
+                                                .toTypedArray(), position=decl.value!!.position)
+                            }
+                            decl.value!!.linkParents(decl)
+                        }
+                    }
                     if(litval?.type==DataType.FLOAT)
                         errors.add(ExpressionError("arraysize requires only integers here", litval.position))
                     if(decl.arraysize==null)
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 80e3460f1..f89350245 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -60,7 +60,7 @@ of values together (and use it multiple times). Something like::
 
     struct Point {
         ubyte   color
-        word[3] vec = [0,0,0]
+        word[] vec = [0,0,0]
     }
 
     Point p1
diff --git a/examples/test.p8 b/examples/test.p8
index 45dbb7de6..c51ee910f 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -4,16 +4,15 @@
 
     sub start() {
 
-        ; @todo documentation on array without size
-
         ubyte[5] array2 =  20 to 100        ; @todo fix this initializer value
         word[5] array3 = 3000 to 3100       ; @todo fix this initializer value
-        byte[] derp = 99                    ; @todo better ast error
 
         c64scr.print_uw(len(array2))
         c64.CHROUT('\n')
         c64scr.print_uw(len(array3))
         c64.CHROUT('\n')
+        c64scr.print_uw(len(array4))
+        c64.CHROUT('\n')
         c64.CHROUT('\n')
         c64scr.print_ub(array2[0])
         c64.CHROUT(',')