diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index d0047c5..4ca8337 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -967,6 +967,7 @@
     DCHECK(last_instruction_ == nullptr);
     first_instruction_ = last_instruction_ = instruction;
   } else {
+    DCHECK(last_instruction_ != nullptr);
     last_instruction_->next_ = instruction;
     instruction->previous_ = last_instruction_;
     last_instruction_ = instruction;