diff --git a/src/squeaknim.nim b/src/squeaknim.nim
index 2024f1b..d8fa6f6 100644
--- a/src/squeaknim.nim
+++ b/src/squeaknim.nim
@@ -10,12 +10,15 @@ const
 var
   dllName {.compileTime.}: string = "SqueakNimTest"
   stCode {.compileTime.}: string = ""
+  gPrefix {.compileTime.}: string = ""
 
-template setModulename*(s: string) =
+template setModulename*(s, prefix: string) =
   ## Sets the DLL name. This is also used to set the 'category' in the generated
-  ## classes.
+  ## classes. 'prefix' is added to every generated class that wraps a Nim
+  ## object.
   static:
     dllName = s
+    gPrefix = prefix
 
 template writeExternalLibrary*() =
   static:
@@ -37,22 +40,8 @@ template writeSmallTalkCode*(filename: string) =
 proc mapTypeToC(symbolicType: NimNode): string {.compileTime.} =
   let t = symbolicType.getType
   if symbolicType.kind == nnkSym and t.typeKind == ntyObject:
-    return $symbolicType
+    return gPrefix & $symbolicType
   case t.typeKind
-  of ntyTuple:
-    result = $t
-    when false:
-      let tt = if t.kind == nnkBracketExpr: t else: t.getType
-      expectKind t, nnkBracketExpr
-      result = "struct {"
-      for i in 0 .. < tt.len:
-        result.addf "$# Field$#;\n", mapTypeToC(tt[i]), $i
-      result.add "}"
-  of ntyArray, ntyArrayConstr:
-    # implement this!
-    result = "XXX"
-  of ntyOpenArray:
-    result = mapTypeToC(t[1]) & "* " & intType
   of ntyPtr, ntyVar:
     expectKind t, nnkBracketExpr
     result = mapTypeToC(t[1]) & "*"
@@ -110,17 +99,17 @@ macro exportSt*(className: string; body: stmt): stmt =
       apicall.add(mapTypeToC(typ))
       inc counter
   apicall.add(") module: '" & dllName & "'>\n" &
-              " ^self externalCallFailed.\n")
-  stCode.add(st & "\n\"Generated by NimSqueak\"\n" & apicall)
+              "\t^self externalCallFailed.\n")
+  stCode.add(st & "\n\t\"Generated by NimSqueak\"\n\t" & apicall)
 
-macro wrapObject*(name: string; typ: stmt): stmt =
+macro wrapObject*(typ: stmt): stmt =
   ## Declares a SmallTalk wrapper class.
-  let name = name.strVal.capitalize
   var t = typ.getType()
   if t.typeKind == ntyTypeDesc:
     expectKind t, nnkBracketExpr
     t = t[1]
-
+  expectKind t, nnkSym
+  let name = gPrefix & ($t).capitalize
   if t.kind != nnkObjectTy: t = t.getType
   expectKind t, nnkObjectTy
   t = t[1]
@@ -128,7 +117,7 @@ macro wrapObject*(name: string; typ: stmt): stmt =
   var fields = ""
   for i in 0.. < t.len:
     expectKind t[i], nnkSym
-    fields.addf "($# '$#')\n", $t[i], mapTypeToC(t[i])
+    fields.addf "\t($# '$#')\n", $t[i], mapTypeToC(t[i])
 
   let st = """ExternalStructure subclass: #$1
     instanceVariableNames: ''
@@ -142,10 +131,9 @@ $1 class
   !$1 class methodsFor: 'field definition' stamp: 'SqueakNim'!
   fields
    ^#(
-   $3
+$3
    )! !
 
-  $1 compileFields!
   $1 defineFields.
 
 """ % [name, dllName, fields]
diff --git a/tests/test1.nim b/tests/test1.nim
index bf0bf21..992d136 100644
--- a/tests/test1.nim
+++ b/tests/test1.nim
@@ -6,13 +6,13 @@ type
   Vector3 = object
     x, y, z: MyFloat
 
-setModulename "urhonimo"
+setModulename "urhonimo", "UR"
 
-wrapObject("Vector3", Vector3)
+wrapObject(Vector3)
 
 writeExternalLibrary()
 
-proc foo(a, b: Vector3; c: openArray[int]): cstring {.exportSt: "bar".} =
+proc foo(a, b: Vector3): cstring {.exportSt: "bar".} =
   result = "some string here"
 
 writeSmallTalkCode("test1.st")