diff --git a/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
index 23bee12eb..ce5ea111c 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/AsmGen.kt
@@ -684,7 +684,7 @@ internal class AsmGen(private val program: Program,
 +""")
                 when(register) {
                     CpuRegister.A -> out("  inx |  lda  P8ESTACK_LO,x")
-                    CpuRegister.X -> throw AssemblyError("can't use X here")
+                    CpuRegister.X -> out("  inx |  lda  P8ESTACK_LO,x |  tax")
                     CpuRegister.Y -> out("  inx |  ldy  P8ESTACK_LO,x")
                 }
             }
@@ -722,7 +722,7 @@ internal class AsmGen(private val program: Program,
                 expressionsAsmGen.translateExpression(index)
                 when(register) {
                     CpuRegister.A -> out("  inx |  lda  P8ESTACK_LO,x")
-                    CpuRegister.X -> throw AssemblyError("can't use X here")
+                    CpuRegister.X -> out("  inx |  lda  P8ESTACK_LO,x |  tax")
                     CpuRegister.Y -> out("  inx |  ldy  P8ESTACK_LO,x")
                 }
             }
diff --git a/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
index 704cf505a..96c1c0247 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/FunctionCallAsmGen.kt
@@ -4,6 +4,7 @@ import prog8.ast.IFunctionCall
 import prog8.ast.Program
 import prog8.ast.base.*
 import prog8.ast.expressions.*
+import prog8.ast.statements.RegisterOrStatusflag
 import prog8.ast.statements.Subroutine
 import prog8.ast.statements.SubroutineParameter
 import prog8.compiler.AssemblyError
@@ -63,9 +64,21 @@ internal class FunctionCallAsmGen(private val program: Program, private val asmg
     private fun registerArgsViaStackEvaluation(stmt: IFunctionCall, sub: Subroutine) {
         // this is called when one or more of the arguments are 'complex' and
         // cannot be assigned to a register easily or risk clobbering other registers.
-        for (arg in stmt.args.reversed())
-            asmgen.translateExpression(arg)
-        for (regparam in sub.asmParameterRegisters) {
+
+        // make sure the X register is loaded last so we can "safely" destroy the estack pointer
+        val argsOrig = stmt.args.zip(sub.asmParameterRegisters)
+        val args = mutableListOf<Pair<Expression, RegisterOrStatusflag>>()
+        for(argOrig in argsOrig) {
+            if(argOrig.second.registerOrPair in setOf(RegisterOrPair.X, RegisterOrPair.AX, RegisterOrPair.XY))
+                args.add(argOrig)
+            else
+                args.add(0, argOrig)
+        }
+
+        for (arg in args.reversed())
+            asmgen.translateExpression(arg.first)
+        for (arg in args) {
+            val regparam = arg.second
             when {
                 regparam.statusflag==Statusflag.Pc -> {
                     asmgen.out("""
diff --git a/compiler/src/prog8/compiler/target/c64/codegen/assignment/AssignmentAsmGen.kt b/compiler/src/prog8/compiler/target/c64/codegen/assignment/AssignmentAsmGen.kt
index 77c5d3b3b..5905c0b41 100644
--- a/compiler/src/prog8/compiler/target/c64/codegen/assignment/AssignmentAsmGen.kt
+++ b/compiler/src/prog8/compiler/target/c64/codegen/assignment/AssignmentAsmGen.kt
@@ -260,16 +260,16 @@ internal class AssignmentAsmGen(private val program: Program, private val asmgen
                     DataType.UBYTE, DataType.BYTE -> {
                         when(target.register!!) {
                             RegisterOrPair.A -> asmgen.out(" inx |  lda  P8ESTACK_LO,x")
-                            RegisterOrPair.X -> throw AssemblyError("can't use X here")
+                            RegisterOrPair.X -> asmgen.out(" inx |  lda  P8ESTACK_LO,x |  tax")
                             RegisterOrPair.Y -> asmgen.out(" inx |  ldy  P8ESTACK_LO,x")
                             else -> throw AssemblyError("can't assign byte to register pair word")
                         }
                     }
                     DataType.UWORD, DataType.WORD, in PassByReferenceDatatypes -> {
                         when(target.register!!) {
-                            RegisterOrPair.AX -> throw AssemblyError("can't use X here")
+                            RegisterOrPair.AX -> asmgen.out(" inx |  lda  P8ESTACK_LO,x |  pha  |  lda  P8ESTACK_HI,x |  tax |  pla")
                             RegisterOrPair.AY-> asmgen.out(" inx |  lda  P8ESTACK_LO,x |  ldy  P8ESTACK_HI,x")
-                            RegisterOrPair.XY-> throw AssemblyError("can't use X here")
+                            RegisterOrPair.XY-> asmgen.out(" inx |  lda  P8ESTACK_LO,x |  ldy  P8ESTACK_HI,x |  tax")
                             else -> throw AssemblyError("can't assign word to single byte register")
                         }
                     }
@@ -590,7 +590,7 @@ internal class AssignmentAsmGen(private val program: Program, private val asmgen
             TargetStorageKind.STACK -> {
                 when(register) {
                     CpuRegister.A -> asmgen.out(" sta  P8ESTACK_LO,x |  dex")
-                    CpuRegister.X -> throw AssemblyError("can't use X here")
+                    CpuRegister.X -> throw AssemblyError("can't store X itself on eval stack")
                     CpuRegister.Y -> asmgen.out(" tya |  sta  P8ESTACK_LO,x |  dex")
                 }
             }