diff --git a/compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt b/compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt
index 388aff06f..b3515b8fd 100644
--- a/compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt
+++ b/compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt
@@ -202,14 +202,14 @@ private class AsmSubroutineReturn(val type: DataType,
 
 private fun Prog8ANTLRParser.Asmsub_returnsContext.toAst(): List<AsmSubroutineReturn>
         = asmsub_return().map {
-            val register = it.register().text
+            val register = it.register.text
             var registerorpair: RegisterOrPair? = null
             var statusregister: Statusflag? = null
             if(register!=null) {
                 when (register) {
                     in RegisterOrPair.names -> registerorpair = RegisterOrPair.valueOf(register)
                     in Statusflag.names -> statusregister = Statusflag.valueOf(register)
-                    else -> throw FatalAstException("invalid register or status flag in $it")
+                    else -> throw SyntaxError("invalid register or status flag", toPosition())
                 }
             }
             AsmSubroutineReturn(
@@ -224,14 +224,17 @@ private fun Prog8ANTLRParser.Asmsub_paramsContext.toAst(): List<AsmSubroutinePar
     var datatype = vardecl.datatype()?.toAst() ?: DataType.UNDEFINED
     if(vardecl.ARRAYSIG()!=null || vardecl.arrayindex()!=null)
         datatype = ElementToArrayTypes.getValue(datatype)
-    val register = it.register().text
+    val register = it.register.text
     var registerorpair: RegisterOrPair? = null
     var statusregister: Statusflag? = null
     if(register!=null) {
         when (register) {
             in RegisterOrPair.names -> registerorpair = RegisterOrPair.valueOf(register)
             in Statusflag.names -> statusregister = Statusflag.valueOf(register)
-            else -> throw FatalAstException("invalid register or status flag '$register'")
+            else -> {
+                val p = toPosition()
+                throw SyntaxError("invalid register or status flag", Position(p.file, it.register.line, it.register.charPositionInLine, it.register.charPositionInLine+1))
+            }
         }
     }
     AsmSubroutineParameter(vardecl.varname.text, datatype, registerorpair, statusregister, toPosition())
@@ -314,8 +317,12 @@ private fun Prog8ANTLRParser.Assign_targetContext.toAst() : AssignTarget {
 }
 
 private fun Prog8ANTLRParser.ClobberContext.toAst() : Set<CpuRegister> {
-    val names = this.cpuregister().map { it.text }
-    return names.map { CpuRegister.valueOf(it) }.toSet()
+    val names = this.NAME().map { it.text }
+    try {
+        return names.map { CpuRegister.valueOf(it) }.toSet()
+    } catch(ax: IllegalArgumentException) {
+        throw SyntaxError("invalid pu register", toPosition())
+    }
 }
 
 private fun Prog8ANTLRParser.DatatypeContext.toAst() = DataType.valueOf(text.uppercase())
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 559ee9630..e5f30fe17 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,8 +3,11 @@ TODO
 
 For next minor release
 ^^^^^^^^^^^^^^^^^^^^^^
-- fix IR/VM: animals.p8 example somehow doesn't print the animal name correctly in the first question, and exits after 1 animal instead of looping
+- check that peekw() and peek() and @(...) accept a[i] where a=uword
+- fix pokew() crash with args like: a[i] (where a=uword) ,  z % twoIMinusOne
 - fix Github issue with X register https://github.com/irmen/prog8/issues/94
+- fix Github issue with array problems https://github.com/irmen/prog8/issues/99
+- fix IR/VM: animals.p8 example somehow doesn't print the animal name correctly in the first question, and exits after 1 animal instead of looping
 
 ...
 
diff --git a/parser/antlr/Prog8ANTLR.g4 b/parser/antlr/Prog8ANTLR.g4
index e9ae0ca5f..38c0fb059 100644
--- a/parser/antlr/Prog8ANTLR.g4
+++ b/parser/antlr/Prog8ANTLR.g4
@@ -55,8 +55,6 @@ ARRAYSIG :
     '[]'
     ;
 
-cpuregister: 'A' | 'X' | 'Y';
-register: 'A' | 'X' | 'Y' | 'AX' | 'AY' | 'XY' | 'Pc' | 'Pz' | 'Pn' | 'Pv' | 'R0' | 'R1' | 'R2' | 'R3' | 'R4' | 'R5' | 'R6' | 'R7' | 'R8' | 'R9' | 'R10' | 'R11' | 'R12' | 'R13' | 'R14' | 'R15';
 
 // A module (file) consists of zero or more directives or blocks, in any order.
 // If there are more than one, then they must be separated by EOL (one or more newlines).
@@ -66,7 +64,6 @@ module: EOL* ((directive | block) (EOL+ (directive | block))*)? EOL* EOF;
 
 block: identifier integerliteral? '{' EOL (block_statement | EOL)* '}';
 
-
 block_statement:
 	directive
 	| variabledeclaration
@@ -263,15 +260,15 @@ asmsub_decl : identifier '(' asmsub_params? ')' asmsub_clobbers? asmsub_returns?
 
 asmsub_params :  asmsub_param (',' EOL? asmsub_param)* ;
 
-asmsub_param :  vardecl '@' register ;      // A,X,Y,AX,AY,XY,Pc,Pz,Pn,Pv allowed.
+asmsub_param :  vardecl '@' register=NAME ;      // A,X,Y,AX,AY,XY,Pc,Pz,Pn,Pv allowed.
 
 asmsub_clobbers : 'clobbers' '(' clobber? ')' ;
 
-clobber :  cpuregister (',' cpuregister)* ;       // A,X,Y allowed
+clobber :  NAME (',' NAME)* ;       // A,X,Y allowed
 
 asmsub_returns :  '->' asmsub_return (',' EOL? asmsub_return)* ;
 
-asmsub_return :  datatype '@' register ;     // A,X,Y,AX,AY,XY,Pc,Pz,Pn,Pv allowed
+asmsub_return :  datatype '@' register=NAME ;     // A,X,Y,AX,AY,XY,Pc,Pz,Pn,Pv allowed
 
 
 if_stmt :  'if' expression EOL? (statement | statement_block) EOL? else_part?  ; // statement is constrained later