diff --git a/libraries/chain/controller.cpp b/libraries/chain/controller.cpp
index bafe7933e9d..1b1f914db2d 100644
--- a/libraries/chain/controller.cpp
+++ b/libraries/chain/controller.cpp
@@ -313,6 +313,10 @@ struct controller_impl {
       set_activation_handler<builtin_protocol_feature_t::replace_deferred>();
       set_activation_handler<builtin_protocol_feature_t::get_sender>();
 
+      self.irreversible_block.connect([this](const block_state_ptr& bsp) {
+         wasmif.current_lib(bsp->block_num);
+      });
+
 
 #define SET_APP_HANDLER( receiver, contract, action) \
    set_apply_handler( #receiver, #contract, #action, &BOOST_PP_CAT(apply_, BOOST_PP_CAT(contract, BOOST_PP_CAT(_,action) ) ) )
diff --git a/libraries/chain/eosio_contract.cpp b/libraries/chain/eosio_contract.cpp
index 1fe849abb48..4a18406ee02 100644
--- a/libraries/chain/eosio_contract.cpp
+++ b/libraries/chain/eosio_contract.cpp
@@ -160,6 +160,7 @@ void apply_eosio_setcode(apply_context& context) {
       old_size  = (int64_t)old_code_entry.code.size() * config::setcode_ram_bytes_multiplier;
       if( old_code_entry.code_ref_count == 1 ) {
          db.remove(old_code_entry);
+         context.control.get_wasm_interface().code_block_num_last_used(account.code_hash, account.vm_type, account.vm_version, context.control.head_block_num() + 1);
       } else {
          db.modify(old_code_entry, [](code_object& o) {
             --o.code_ref_count;
diff --git a/libraries/chain/include/eosio/chain/wasm_interface.hpp b/libraries/chain/include/eosio/chain/wasm_interface.hpp
index 5ddea081d48..b5749179a9b 100644
--- a/libraries/chain/include/eosio/chain/wasm_interface.hpp
+++ b/libraries/chain/include/eosio/chain/wasm_interface.hpp
@@ -82,6 +82,12 @@ namespace eosio { namespace chain {
          //validates code -- does a WASM validation pass and checks the wasm against EOSIO specific constraints
          static void validate(const controller& control, const bytes& code);
 
+         //indicate that a particular code probably won't be used after given block_num
+         void code_block_num_last_used(const digest_type& code_hash, const uint8_t& vm_type, const uint8_t& vm_version, const uint32_t& block_num);
+
+         //indicate the current LIB. evicts old cache entries
+         void current_lib(const uint32_t lib);
+
          //Calls apply or error on a given code
          void apply(const digest_type& code_hash, const uint8_t& vm_type, const uint8_t& vm_version, apply_context& context);
 
diff --git a/libraries/chain/include/eosio/chain/wasm_interface_private.hpp b/libraries/chain/include/eosio/chain/wasm_interface_private.hpp
index 362a29e19f0..2f59bccf69f 100644
--- a/libraries/chain/include/eosio/chain/wasm_interface_private.hpp
+++ b/libraries/chain/include/eosio/chain/wasm_interface_private.hpp
@@ -64,6 +64,19 @@ namespace eosio { namespace chain {
          return mem_image;
       }
 
+      void code_block_num_last_used(const digest_type& code_hash, const uint8_t& vm_type, const uint8_t& vm_version, const uint32_t& block_num) {
+         wasm_cache_index::iterator it = wasm_instantiation_cache.find(boost::make_tuple(code_hash, vm_type, vm_version));
+         if(it != wasm_instantiation_cache.end())
+            wasm_instantiation_cache.modify(it, [block_num](wasm_cache_entry& e) {
+               e.last_block_num_used = block_num;
+            });
+      }
+
+      void current_lib(uint32_t lib) {
+         //anything last used before or on the LIB can be evicted
+         wasm_instantiation_cache.get<by_last_block_num>().erase(wasm_instantiation_cache.get<by_last_block_num>().begin(), wasm_instantiation_cache.get<by_last_block_num>().upper_bound(lib));
+      }
+
       const std::unique_ptr<wasm_instantiated_module_interface>& get_instantiated_module( const digest_type& code_hash, const uint8_t& vm_type,
                                                                                  const uint8_t& vm_version, transaction_context& trx_context )
       {
diff --git a/libraries/chain/wasm_interface.cpp b/libraries/chain/wasm_interface.cpp
index 9fd144a3cb1..75682ff4b80 100644
--- a/libraries/chain/wasm_interface.cpp
+++ b/libraries/chain/wasm_interface.cpp
@@ -57,6 +57,14 @@ namespace eosio { namespace chain {
       //Hard: Kick off instantiation in a separate thread at this location
 	 }
 
+   void wasm_interface::code_block_num_last_used(const digest_type& code_hash, const uint8_t& vm_type, const uint8_t& vm_version, const uint32_t& block_num) {
+      my->code_block_num_last_used(code_hash, vm_type, vm_version, block_num);
+   }
+
+   void wasm_interface::current_lib(const uint32_t lib) {
+      my->current_lib(lib);
+   }
+
    void wasm_interface::apply( const digest_type& code_hash, const uint8_t& vm_type, const uint8_t& vm_version, apply_context& context ) {
       my->get_instantiated_module(code_hash, vm_type, vm_version, context.trx_context)->apply(context);
    }