diff --git a/src/common/base_best_hyps.h b/src/common/base_best_hyps.h
index 21025bcd..c07bc287 100644
--- a/src/common/base_best_hyps.h
+++ b/src/common/base_best_hyps.h
@@ -13,7 +13,7 @@ public:
   BestHypsBase() {}
   BestHypsBase(const BestHypsBase&) = delete;
 
-  virtual void operator()(God &god,
+  virtual void operator()(const God &god,
 		std::vector<Beam>& beams,
         const Beam& prevHyps,
         std::vector<size_t>& beamSizes,
diff --git a/src/cpu/decoder/best_hyps.h b/src/cpu/decoder/best_hyps.h
index 2027bad4..7870914c 100644
--- a/src/cpu/decoder/best_hyps.h
+++ b/src/cpu/decoder/best_hyps.h
@@ -23,7 +23,7 @@ struct ProbCompare {
 class BestHyps : public BestHypsBase
 {
 public:
-  void operator()(God &god,
+  void operator()(const God &god,
 		std::vector<Beam>& beams,
         const Beam& prevHyps,
         std::vector<size_t>& beamSizes,
diff --git a/src/gpu/decoder/best_hyps.h b/src/gpu/decoder/best_hyps.h
index d486fc1b..545995e6 100644
--- a/src/gpu/decoder/best_hyps.h
+++ b/src/gpu/decoder/best_hyps.h
@@ -56,7 +56,7 @@ class BestHyps : public BestHypsBase
       return alignments;
     }
 
-    void operator()(God &god,
+    void operator()(const God &god,
     	  std::vector<Beam>& beams,
           const Beam& prevHyps,
           std::vector<size_t>& beamSizes,