diff --git a/src/ripple/app/hook/HookAPI.h b/src/ripple/app/hook/HookAPI.h
index eefe35b8f..4161ed8f8 100644
--- a/src/ripple/app/hook/HookAPI.h
+++ b/src/ripple/app/hook/HookAPI.h
@@ -46,13 +46,13 @@ public:
 
     /// etxn APIs
     Expected<std::shared_ptr<Transaction>, HookReturnCode>
-    emit(Slice txBlob) const;
+    emit(Slice const& txBlob) const;
 
     Expected<uint64_t, HookReturnCode>
     etxn_burden() const;
 
     Expected<uint64_t, HookReturnCode>
-    etxn_fee_base(Slice txBlob) const;
+    etxn_fee_base(Slice const& txBlob) const;
 
     Expected<uint64_t, HookReturnCode>
     etxn_details(uint8_t* out_ptr) const;
@@ -136,7 +136,7 @@ public:
     otxn_slot(uint32_t slot_into) const;
 
     Expected<Blob, HookReturnCode>
-    otxn_param(Bytes param_name) const;
+    otxn_param(Bytes const& param_name) const;
 
     /// hook APIs
     AccountID
diff --git a/src/ripple/app/hook/impl/HookAPI.cpp b/src/ripple/app/hook/impl/HookAPI.cpp
index 5d955152f..d47b59f94 100644
--- a/src/ripple/app/hook/impl/HookAPI.cpp
+++ b/src/ripple/app/hook/impl/HookAPI.cpp
@@ -364,7 +364,7 @@ HookAPI::otxn_slot(uint32_t slot_into) const
 }
 
 Expected<Blob, HookReturnCode>
-HookAPI::otxn_param(Bytes param_name) const
+HookAPI::otxn_param(Bytes const& param_name) const
 {
     if (param_name.size() < 1)
         return Unexpected(TOO_SMALL);
@@ -567,7 +567,7 @@ HookAPI::hook_pos() const
 }
 
 Expected<std::shared_ptr<Transaction>, HookReturnCode>
-HookAPI::emit(Slice txBlob) const
+HookAPI::emit(Slice const& txBlob) const
 {
     auto& applyCtx = hookCtx.applyCtx;
     auto j = applyCtx.app.journal("View");
@@ -896,7 +896,7 @@ HookAPI::etxn_burden() const
 }
 
 Expected<uint64_t, HookReturnCode>
-HookAPI::etxn_fee_base(ripple::Slice txBlob) const
+HookAPI::etxn_fee_base(ripple::Slice const& txBlob) const
 {
     auto& applyCtx = hookCtx.applyCtx;
     auto j = applyCtx.app.journal("View");