diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 5a27d86218..3208403d48 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -198,8 +198,9 @@ proc semConv(c: PContext, n: PNode): PNode =
       # separate proc from fitNode?
       if op.kind == nkSym and op.sym.isGenericRoutine:
         result.sons[1] = fitNode(c, result.typ, result.sons[1])
-      elif op.kind == nkPar and targetType.kind == tyTuple:
-        # Set type of each field in case any have type tyEmpty (eg. `@[]`)
+      elif op.kind == nkPar and targetType.kind == tyTuple and
+                op.sons.len > 0 and op.sons[0].kind == nkExprColonExpr:
+        # Tuple conversion: set field types in case any are tyEmpty (eg. `@[]`)
         for i in 0..<op.sons.len:
           op.sons[i][1].typ = targetType.sons[i]
     of convNotNeedeed: