diff --git a/files/con4m/params.nim b/files/con4m/params.nim
index 15b08da..4e89180 100644
--- a/files/con4m/params.nim
+++ b/files/con4m/params.nim
@@ -12,11 +12,20 @@ proc validateParameter*(state: ConfigState, param: ParameterInfo):
       err    = unpack[string](boxOpt.get())
 
     if err != "":
-      return some(text(err))
+      return some(color("error: ", "red") + text(err))
 
   return none(Rope)
 
 
+proc setAndValidateParameter(state: ConfigState, param: ParameterInfo,
+                             value: Option[Box]): bool =
+  param.value = value
+  let err = state.validateParameter(param)
+  if err.isSome():
+    print(err.get())
+    return false
+  return true
+
 proc basicConfigureOneParam(state:     ConfigState,
                             component: ComponentInfo,
                             param:     ParameterInfo) =
@@ -31,6 +40,23 @@ proc basicConfigureOneParam(state:     ConfigState,
   elif param.defaultCb.isSome():
     boxOpt = state.sCall(param.defaultCb.get(), @[])
 
+  if not param.prompt:
+    if boxOpt.isNone():
+      print(atom("Non-prompting parameter ") + em(param.name) +
+            text(" does not define a default value either as literal or callback. ") +
+            text("Please manually provide value:"))
+      boxOpt = none(Box)
+    else:
+      if state.setAndValidateParameter(param, boxOpt):
+        return
+      else:
+        # if the default is invalid, even though its non-prompting param
+        # fallback to manual user input to allow to fix the value
+        print(color("error: ", "red") + text("Non-prompting parameter ") +
+              em(param.name) + text(" does not have valid default value. ") +
+              text("Please manually fix it:"))
+        boxOpt = none(Box)
+
   if boxOpt.isSome():
     default = h2(atom("Default is: ") +
                   fgColor(param.defaultType.oneArgToString(boxOpt.get()),
@@ -65,15 +91,9 @@ proc basicConfigureOneParam(state:     ConfigState,
       let f = float(unpack[int](box))
       boxOpt = some(pack(f))
 
-    param.value = boxOpt
-
-    let err = state.validateParameter(param)
-
-    if err.isNone():
+    if state.setAndValidateParameter(param, boxOpt):
       break
 
-    print(err.get())
-
 proc basicConfigureParameters*(state:         ConfigState,
                                component:     ComponentInfo,
                                componentList: seq[ComponentInfo],
diff --git a/files/con4m/treecheck.nim b/files/con4m/treecheck.nim
index 1ec5088..93aa861 100644
--- a/files/con4m/treecheck.nim
+++ b/files/con4m/treecheck.nim
@@ -1038,7 +1038,7 @@ proc checkNode(node: Con4mNode, s: ConfigState) =
     # aren't going to be interpreted in the way they are in any other
     # part of a program.
     const
-      validParamProps = ["doc", "shortdoc", "validator", "default"]
+      validParamProps = ["doc", "shortdoc", "validator", "default", "prompt"]
     var
       foundProps: seq[string]
 
@@ -1078,6 +1078,10 @@ proc checkNode(node: Con4mNode, s: ConfigState) =
           if allowedCallbackType.unify(kid.children[1].typeInfo).isBottom():
             fatal("Callback must be a function that takes no arguments and " &
               "Returns a value of the proper type.")
+      of "prompt":
+        if kid.children[1].kind != NodeSimpLit or
+          boolType.unify(kid.children[1].typeInfo).isBottom():
+            fatal("Prompt must be a boolean")
       of "validator":
         let allowedValidatorType = "(`x) -> string".toCon4mType()
         if kid.children[1].kind != NodeCallbackLit or
@@ -1117,7 +1121,7 @@ proc checkNode(node: Con4mNode, s: ConfigState) =
 
       s.waitingForTypeInfo = true
       var
-        paramObj = ParameterInfo(name: name, defaultType: newTypeVar())
+        paramObj = ParameterInfo(name: name, defaultType: newTypeVar(), prompt: true)
         assnNodes: seq[Con4mNode]
 
       if len(node.children) > 1:
@@ -1140,6 +1144,13 @@ proc checkNode(node: Con4mNode, s: ConfigState) =
           if paramobj.defaultType.unify(callback.tInfo.params[0]).isBottom():
             fatal2Type("Validator parameter does not match inferred type",
                        assignNode, paramObj.defaultType, callback.tInfo)
+        of "prompt":
+          let defType = assignNode.children[1].typeInfo
+          if defType.kind == TypeBool:
+            paramObj.prompt = unpack[bool](assignNode.children[1].value)
+          else:
+            fatal2Type("Prompt value needs to be a boolean",
+                       assignNode, paramObj.defaultType, defType)
         of "default":
           let defType = assignNode.children[1].typeInfo
 
diff --git a/files/con4m/types.nim b/files/con4m/types.nim
index 21fad72..04b7671 100644
--- a/files/con4m/types.nim
+++ b/files/con4m/types.nim
@@ -320,6 +320,7 @@ type
     defaultType*:   Con4mType
     defaultCb*:     Option[CallbackObj]
     value*:         Option[Box]
+    prompt*:        bool # wheter to prompt user for the value or use default only
 
 let
   # These are just shared instances for types that aren't