diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 3f225f3..d1fba31 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -1231,7 +1231,7 @@
     }
   }
   LOG(FATAL) << "Did not find an order between two instructions of the same block.";
-  return true;
+  UNREACHABLE();
 }
 
 bool HInstruction::StrictlyDominates(HInstruction* other_instruction) const {
@@ -1254,7 +1254,7 @@
       } else {
         // There is no order among phis.
         LOG(FATAL) << "There is no dominance between phis of a same block.";
-        return false;
+        UNREACHABLE();
       }
     } else {
       // `this` is not a phi.