diff --git a/src/main/scala/millfork/env/Environment.scala b/src/main/scala/millfork/env/Environment.scala
index a7888e3d..66e2828a 100644
--- a/src/main/scala/millfork/env/Environment.scala
+++ b/src/main/scala/millfork/env/Environment.scala
@@ -694,9 +694,9 @@ class Environment(val parent: Option[Environment], val prefix: String) {
     }
   }
 
-  private def checkName[T <: Thing : Manifest](name: String, pos: Option[Position]): Unit = {
+  private def checkName[T <: Thing : Manifest](objType: String, name: String, pos: Option[Position]): Unit = {
     if (maybeGet[T](name).isEmpty) {
-      ErrorReporting.error(s"`$name` is not defined", pos)
+      ErrorReporting.error(s"$objType `$name` is not defined", pos)
     }
   }
 
@@ -707,9 +707,10 @@ class Environment(val parent: Option[Environment], val prefix: String) {
     case _:DeclarationStatement => ()
     case s:Statement => nameCheck(s.getAllExpressions)
     case _:LiteralExpression => ()
-    case VariableExpression(name) => checkName[Thing](name, node.position)
+    case VariableExpression(name) =>
+      checkName[VariableLikeThing]("Variable or constant", name, node.position)
     case IndexedExpression(name, index) =>
-      checkName[Thing](name, node.position)
+      checkName[IndexableThing]("Array or pointer", name, node.position)
       nameCheck(index)
     case SeparateBytesExpression(h, l) =>
       nameCheck(h)
@@ -718,7 +719,7 @@ class Environment(val parent: Option[Environment], val prefix: String) {
       nameCheck(params.map(_._2))
     case FunctionCallExpression(name, params) =>
       if (name.exists(_.isLetter) && name != "not") {
-        checkName[MangledFunction](name, node.position)
+        checkName[CallableThing]("Function or type", name, node.position)
       }
       nameCheck(params)
   }
diff --git a/src/main/scala/millfork/env/Thing.scala b/src/main/scala/millfork/env/Thing.scala
index b3ca587f..bf1e3345 100644
--- a/src/main/scala/millfork/env/Thing.scala
+++ b/src/main/scala/millfork/env/Thing.scala
@@ -8,7 +8,13 @@ sealed trait Thing {
   def name: String
 }
 
-sealed trait Type extends Thing {
+sealed trait CallableThing extends Thing
+
+sealed trait VariableLikeThing extends Thing
+
+sealed trait IndexableThing extends Thing
+
+sealed trait Type extends CallableThing {
 
   def size: Int
 
@@ -87,13 +93,13 @@ case class Label(name: String) extends ThingInMemory {
   override def toAddress: MemoryAddressConstant = MemoryAddressConstant(this)
 }
 
-sealed trait Variable extends TypedThing
+sealed trait Variable extends TypedThing with VariableLikeThing
 
 case class BlackHole(typ: Type) extends Variable {
   override def name = "<black hole>"
 }
 
-sealed trait VariableInMemory extends Variable with ThingInMemory {
+sealed trait VariableInMemory extends Variable with ThingInMemory with IndexableThing {
 
   def zeropage: Boolean
 }
@@ -144,7 +150,7 @@ case class InitializedMemoryVariable(name: String, address: Option[Constant], ty
   override def alloc: VariableAllocationMethod.Value = VariableAllocationMethod.Static
 }
 
-trait MfArray extends ThingInMemory
+trait MfArray extends ThingInMemory with IndexableThing
 
 case class UninitializedArray(name: String, sizeInBytes: Int) extends MfArray with UninitializedMemory {
   override def toAddress: MemoryAddressConstant = MemoryAddressConstant(this)
@@ -164,8 +170,7 @@ case class RelativeVariable(name: String, address: Constant, typ: Type, zeropage
   override def toAddress: Constant = address
 }
 
-
-sealed trait MangledFunction extends Thing {
+sealed trait MangledFunction extends CallableThing {
   def name: String
 
   def returnType: Type
@@ -218,7 +223,7 @@ case class NormalFunction(name: String,
   override def shouldGenerate = true
 }
 
-case class ConstantThing(name: String, value: Constant, typ: Type) extends TypedThing
+case class ConstantThing(name: String, value: Constant, typ: Type) extends TypedThing with VariableLikeThing with IndexableThing
 
 trait ParamSignature {
   def types: List[Type]