diff --git a/compiler/dfa.nim b/compiler/dfa.nim
index 5eef04148..968b16945 100644
--- a/compiler/dfa.nim
+++ b/compiler/dfa.nim
@@ -594,11 +594,12 @@ proc genCall(c: var Con; n: PNode) =
   inc c.inCall
   for i in 1..<n.len:
     gen(c, n[i])
-    if t != nil and i < t.len and t.sons[i].kind == tyVar:
-      # XXX This is wrong! Pass by var is a 'might def', not a 'must def'
-      # like the other defs we emit. This is not good enough for a move
-      # optimizer.
-      genDef(c, n[i])
+    when false:
+      if t != nil and i < t.len and t.sons[i].kind == tyVar:
+        # XXX This is wrong! Pass by var is a 'might def', not a 'must def'
+        # like the other defs we emit. This is not good enough for a move
+        # optimizer.
+        genDef(c, n[i])
   # every call can potentially raise:
   if c.inTryStmt > 0 and canRaise(n[0]):
     # we generate the instruction sequence: