diff --git a/compiler/msgs.nim b/compiler/msgs.nim
index 923c351703..be69f1ea5f 100644
--- a/compiler/msgs.nim
+++ b/compiler/msgs.nim
@@ -113,7 +113,7 @@ type
     warnSmallLshouldNotBeUsed, warnUnknownMagic, warnRedefinitionOfLabel, 
     warnUnknownSubstitutionX, warnLanguageXNotSupported,
     warnFieldXNotSupported, warnCommentXIgnored, 
-    warnNilStatement, warnAnalysisLoophole,
+    warnNilStatement, warnTypelessParam,
     warnDifferentHeaps, warnWriteToForeignHeap, warnUnsafeCode,
     warnEachIdentIsTuple, warnShadowIdent, 
     warnProveInit, warnProveField, warnProveIndex, warnGcUnsafe, warnGcUnsafe2,
@@ -376,7 +376,7 @@ const
     warnFieldXNotSupported: "field \'$1\' not supported [FieldXNotSupported]", 
     warnCommentXIgnored: "comment \'$1\' ignored [CommentXIgnored]", 
     warnNilStatement: "'nil' statement is deprecated; use an empty 'discard' statement instead [NilStmt]", 
-    warnAnalysisLoophole: "thread analysis incomplete due to unknown call '$1' [AnalysisLoophole]",
+    warnTypelessParam: "'$1' has no type. Typeless parameters are deprecated; only allowed for 'template' [TypelessParam]",
     warnDifferentHeaps: "possible inconsistency of thread local heaps [DifferentHeaps]",
     warnWriteToForeignHeap: "write to foreign heap [WriteToForeignHeap]",
     warnUnsafeCode: "unsafe code: '$1' [UnsafeCode]",
@@ -418,7 +418,7 @@ const
     "RedefinitionOfLabel", "UnknownSubstitutionX",
     "LanguageXNotSupported", "FieldXNotSupported",
     "CommentXIgnored", "NilStmt",
-    "AnalysisLoophole", "DifferentHeaps", "WriteToForeignHeap",
+    "TypelessParam", "DifferentHeaps", "WriteToForeignHeap",
     "UnsafeCode", "EachIdentIsTuple", "ShadowIdent", 
     "ProveInit", "ProveField", "ProveIndex", "GcUnsafe", "GcUnsafe2", "Uninit",
     "GcMem", "Destructor", "LockLevel", "User"]
diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 7908742dbe..d052700b20 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -911,6 +911,8 @@ proc semProcTypeNode(c: PContext, n, genericParams: PNode,
     if not hasType and not hasDefault:
       if isType: localError(a.info, "':' expected")
       let tdef = if kind in {skTemplate, skMacro}: tyExpr else: tyAnything
+      if tdef == tyAnything:
+        message(a.info, warnTypelessParam, renderTree(n))
       typ = newTypeS(tdef, c)
 
     if skipTypes(typ, {tyGenericInst}).kind == tyEmpty: continue