diff --git a/src/binaryen.cpp b/src/binaryen.cpp
index 6429f437d..ab3c7dc33 100644
--- a/src/binaryen.cpp
+++ b/src/binaryen.cpp
@@ -29,11 +29,44 @@
 #include "eei.h"
 #include "exceptions.h"
 
+#include "shell-interface.h"
+
 using namespace std;
 using namespace wasm;
 
 namespace hera {
 
+class BinaryenEthereumInterface : public wasm::ShellExternalInterface, EthereumInterface {
+public:
+  explicit BinaryenEthereumInterface(
+    evmc_context* _context,
+    vector<uint8_t> const& _code,
+    evmc_message const& _msg,
+    ExecutionResult & _result,
+    bool _meterGas
+  ):
+    ShellExternalInterface(),
+    EthereumInterface(_context, _code, _msg, _result, _meterGas)
+  { }
+
+protected:
+  wasm::Literal callImport(wasm::Import *import, wasm::LiteralList& arguments) override;
+#if HERA_DEBUGGING
+  wasm::Literal callDebugImport(wasm::Import *import, wasm::LiteralList& arguments);
+#endif
+
+  void importGlobals(map<wasm::Name, wasm::Literal>& globals, wasm::Module& wasm) override;
+
+  void trap(const char* why) override {
+    ensureCondition(false, VMTrap, why);
+  }
+
+private:
+  size_t memorySize() const override { return memory.size(); }
+  void memorySet(size_t offset, uint8_t value) override { memory.set<uint8_t>(offset, value); }
+  uint8_t memoryGet(size_t offset) override { return memory.get<uint8_t>(offset); }
+};
+
   void BinaryenEthereumInterface::importGlobals(map<Name, Literal>& globals, Module& wasm) {
     (void)globals;
     (void)wasm;
@@ -434,40 +467,6 @@ namespace hera {
     heraAssert(false, string("Unsupported import called: ") + import->module.str + "::" + import->base.str + " (" + to_string(arguments.size()) + "arguments)");
   }
 
-// NOTE: This should be caught during deployment time by the Sentinel.
-void BinaryenEngine::validate_contract(Module & module)
-{
-  ensureCondition(
-    module.getExportOrNull(Name("main")) != nullptr,
-    ContractValidationFailure,
-    "Contract entry point (\"main\") missing."
-  );
-
-  ensureCondition(
-    module.getExportOrNull(Name("memory")) != nullptr,
-    ContractValidationFailure,
-    "Contract export (\"memory\") missing."
-  );
-
-  ensureCondition(
-    module.exports.size() == 2,
-    ContractValidationFailure,
-    "Contract exports more than (\"main\") and (\"memory\")."
-  );
-
-  for (auto const& import: module.imports) {
-    ensureCondition(
-      import->module == Name("ethereum")
-#if HERA_DEBUGGING
-      || import->module == Name("debug")
-#endif
-      ,
-      ContractValidationFailure,
-      "Import from invalid namespace."
-    );
-  }
-}
-
 unique_ptr<WasmEngine> BinaryenEngine::create()
 {
   return unique_ptr<WasmEngine>{new BinaryenEngine};
@@ -504,8 +503,36 @@ ExecutionResult BinaryenEngine::execute(
     "Module is not valid."
   );
 
-  // NOTE: This should be caught during deployment time by the Sentinel.
-  validate_contract(module);
+  // NOTE: Most of this should be caught during deployment time by the Sentinel.
+  ensureCondition(
+    module.getExportOrNull(Name("main")) != nullptr,
+    ContractValidationFailure,
+    "Contract entry point (\"main\") missing."
+  );
+
+  ensureCondition(
+    module.getExportOrNull(Name("memory")) != nullptr,
+    ContractValidationFailure,
+    "Contract export (\"memory\") missing."
+  );
+
+  ensureCondition(
+    module.exports.size() == 2,
+    ContractValidationFailure,
+    "Contract exports more than (\"main\") and (\"memory\")."
+  );
+
+  for (auto const& import: module.imports) {
+    ensureCondition(
+      import->module == Name("ethereum")
+#if HERA_DEBUGGING
+      || import->module == Name("debug")
+#endif
+      ,
+      ContractValidationFailure,
+      "Import from invalid namespace."
+    );
+  }
 
   // NOTE: DO NOT use the optimiser here, it will conflict with metering
 
diff --git a/src/binaryen.h b/src/binaryen.h
index 92b492c8d..6054d6ad2 100644
--- a/src/binaryen.h
+++ b/src/binaryen.h
@@ -16,49 +16,12 @@
 
 #pragma once
 
-#include <wasm.h>
-#include <wasm-binary.h>
-
 #include "eei.h"
 
-#include "shell-interface.h"
-
 namespace hera {
 
-class BinaryenEthereumInterface : public wasm::ShellExternalInterface, EthereumInterface {
-public:
-  explicit BinaryenEthereumInterface(
-    evmc_context* _context,
-    std::vector<uint8_t> const& _code,
-    evmc_message const& _msg,
-    ExecutionResult & _result,
-    bool _meterGas
-  ):
-    ShellExternalInterface(),
-    EthereumInterface(_context, _code, _msg, _result, _meterGas)
-  { }
-
-protected:
-  wasm::Literal callImport(wasm::Import *import, wasm::LiteralList& arguments) override;
-#if HERA_DEBUGGING
-  wasm::Literal callDebugImport(wasm::Import *import, wasm::LiteralList& arguments);
-#endif
-
-  void importGlobals(std::map<wasm::Name, wasm::Literal>& globals, wasm::Module& wasm) override;
-
-  void trap(const char* why) override {
-    ensureCondition(false, VMTrap, why);
-  }
-
-private:
-  size_t memorySize() const override { return memory.size(); }
-  void memorySet(size_t offset, uint8_t value) override { memory.set<uint8_t>(offset, value); }
-  uint8_t memoryGet(size_t offset) override { return memory.get<uint8_t>(offset); }
-};
-
 class BinaryenEngine : public WasmEngine {
 public:
-
   /// Factory method to create the Binaryen Wasm Engine.
   static std::unique_ptr<WasmEngine> create();
 
@@ -69,9 +32,6 @@ class BinaryenEngine : public WasmEngine {
     evmc_message const& msg,
     bool meterInterfaceGas
   ) override;
-
-private:
-  static void validate_contract(wasm::Module & module);
 };
 
 }
diff --git a/src/hera.cpp b/src/hera.cpp
index b9a09d2ac..ed4405333 100644
--- a/src/hera.cpp
+++ b/src/hera.cpp
@@ -16,6 +16,8 @@
 
 #include <hera/hera.h>
 
+#include <limits>
+#include <cstring>
 #include <vector>
 #include <unistd.h>
 #include <iostream>
diff --git a/src/wabt.cpp b/src/wabt.cpp
index d818815ea..3f0db8edd 100644
--- a/src/wabt.cpp
+++ b/src/wabt.cpp
@@ -41,6 +41,148 @@ using namespace wabt;
 
 namespace hera {
 
+class WabtEthereumInterface : EthereumInterface, public wabt::interp::HostImportDelegate {
+public:
+  explicit WabtEthereumInterface(
+    evmc_context* _context,
+    vector<uint8_t> const& _code,
+    evmc_message const& _msg,
+    ExecutionResult & _result,
+    bool _meterGas
+  ):
+    EthereumInterface(_context, _code, _msg, _result, _meterGas)
+  {}
+
+  // TODO: improve this design...
+  void setWasmMemory(wabt::interp::Memory* _wasmMemory) {
+    m_wasmMemory = _wasmMemory;
+  }
+
+protected:
+  wabt::Result ImportFunc(
+    wabt::interp::FuncImport* import,
+    wabt::interp::Func* func,
+    wabt::interp::FuncSignature* func_sig,
+    const ErrorCallback& callback
+  ) override;
+
+  wabt::Result ImportMemory(
+    wabt::interp::MemoryImport* import,
+    wabt::interp::Memory* mem,
+    const ErrorCallback& callback
+  ) override;
+
+  wabt::Result ImportGlobal(
+    wabt::interp::GlobalImport* import,
+    wabt::interp::Global* global,
+    const ErrorCallback& callback
+  ) override;
+
+  wabt::Result ImportTable(
+    wabt::interp::TableImport* import,
+    wabt::interp::Table* table,
+    const ErrorCallback& callback
+  ) override;
+
+  static wabt::interp::Result wabtUseGas(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtGetGasLeft(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtStorageStore(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtStorageLoad(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtFinish(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtRevert(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtGetCallDataSize(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtCallDataCopy(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+  static wabt::interp::Result wabtGetCallValue(
+    const wabt::interp::HostFunc* func,
+    const wabt::interp::FuncSignature* sig,
+    wabt::Index num_args,
+    wabt::interp::TypedValue* args,
+    wabt::Index num_results,
+    wabt::interp::TypedValue* out_results,
+    void* user_data
+  );
+
+private:
+  // These assume that m_wasmMemory was set prior to execution.
+  size_t memorySize() const override { return m_wasmMemory->data.size(); }
+  void memorySet(size_t offset, uint8_t value) override { m_wasmMemory->data[offset] = static_cast<char>(value); }
+  uint8_t memoryGet(size_t offset) override { return static_cast<uint8_t>(m_wasmMemory->data[offset]); }
+
+  wabt::interp::Memory* m_wasmMemory;
+};
+
 unique_ptr<WasmEngine> WabtEngine::create()
 {
   return unique_ptr<WasmEngine>{new WabtEngine};
diff --git a/src/wabt.h b/src/wabt.h
index 23c0bdd30..34d8b819e 100644
--- a/src/wabt.h
+++ b/src/wabt.h
@@ -16,157 +16,12 @@
 
 #pragma once
 
-#include <src/interp.h>
-
 #include "eei.h"
 
 namespace hera {
 
-class WabtEthereumInterface : EthereumInterface, public wabt::interp::HostImportDelegate {
-public:
-  explicit WabtEthereumInterface(
-    evmc_context* _context,
-    std::vector<uint8_t> const& _code,
-    evmc_message const& _msg,
-    ExecutionResult & _result,
-    bool _meterGas
-  ):
-    EthereumInterface(_context, _code, _msg, _result, _meterGas)
-  {}
-
-  // TODO: improve this design...
-  void setWasmMemory(wabt::interp::Memory* _wasmMemory) {
-    m_wasmMemory = _wasmMemory;
-  }
-
-protected:
-  wabt::Result ImportFunc(
-    wabt::interp::FuncImport* import,
-    wabt::interp::Func* func,
-    wabt::interp::FuncSignature* func_sig,
-    const ErrorCallback& callback
-  ) override;
-
-  wabt::Result ImportMemory(
-    wabt::interp::MemoryImport* import,
-    wabt::interp::Memory* mem,
-    const ErrorCallback& callback
-  ) override;
-
-  wabt::Result ImportGlobal(
-    wabt::interp::GlobalImport* import,
-    wabt::interp::Global* global,
-    const ErrorCallback& callback
-  ) override;
-
-  wabt::Result ImportTable(
-    wabt::interp::TableImport* import,
-    wabt::interp::Table* table,
-    const ErrorCallback& callback
-  ) override;
-
-  static wabt::interp::Result wabtUseGas(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtGetGasLeft(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtStorageStore(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtStorageLoad(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtFinish(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtRevert(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtGetCallDataSize(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtCallDataCopy(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-  static wabt::interp::Result wabtGetCallValue(
-    const wabt::interp::HostFunc* func,
-    const wabt::interp::FuncSignature* sig,
-    wabt::Index num_args,
-    wabt::interp::TypedValue* args,
-    wabt::Index num_results,
-    wabt::interp::TypedValue* out_results,
-    void* user_data
-  );
-
-private:
-  // These assume that m_wasmMemory was set prior to execution.
-  size_t memorySize() const override { return m_wasmMemory->data.size(); }
-  void memorySet(size_t offset, uint8_t value) override { m_wasmMemory->data[offset] = static_cast<char>(value); }
-  uint8_t memoryGet(size_t offset) override { return static_cast<uint8_t>(m_wasmMemory->data[offset]); }
-
-  wabt::interp::Memory* m_wasmMemory;
-};
-
 class WabtEngine : public WasmEngine {
 public:
-
   /// Factory method to create the WABT Wasm Engine.
   static std::unique_ptr<WasmEngine> create();
 
diff --git a/src/wavm.cpp b/src/wavm.cpp
index 2c2576c47..bf363b021 100644
--- a/src/wavm.cpp
+++ b/src/wavm.cpp
@@ -15,7 +15,21 @@
  * limitations under the License.
  */
 
+#include <iostream>
+#include <memory>
+#include <stack>
+
 #include "wavm.h"
+
+#define DLL_IMPORT // Needed by wavm on some platforms
+#include "Inline/Serialization.h"
+#include "IR/Module.h"
+#include "IR/Validate.h"
+#include "Runtime/Intrinsics.h"
+#include "Runtime/Linker.h"
+#include "Runtime/Runtime.h"
+#include "WASM/WASM.h"
+
 #include "debugging.h"
 #include "eei.h"
 #include "exceptions.h"
@@ -27,6 +41,31 @@ using namespace std;
 
 namespace hera {
 
+class WavmEthereumInterface : public EthereumInterface {
+public:
+  explicit WavmEthereumInterface(
+    evmc_context* _context,
+    vector<uint8_t> const& _code,
+    evmc_message const& _msg,
+    ExecutionResult & _result,
+    bool _meterGas
+  ):
+    EthereumInterface(_context, _code, _msg, _result, _meterGas)
+  {}
+
+  void setWasmMemory(Runtime::MemoryInstance* _wasmMemory) {
+    m_wasmMemory = _wasmMemory;
+  }
+
+private:
+  // These assume that m_wasmMemory was set prior to execution.
+  size_t memorySize() const override { return Runtime::getMemoryNumPages(m_wasmMemory) * 65536; }
+  void memorySet(size_t offset, uint8_t value) override { (Runtime::memoryArrayPtr<U8>(m_wasmMemory, offset, 1))[0] = value; }
+  uint8_t memoryGet(size_t offset) override { return (Runtime::memoryArrayPtr<U8>(m_wasmMemory, offset, 1))[0]; }
+
+  Runtime::MemoryInstance* m_wasmMemory;
+};
+
 unique_ptr<WasmEngine> WavmEngine::create()
 {
   return unique_ptr<WasmEngine>{new WavmEngine};
@@ -147,6 +186,19 @@ namespace wavm_host_module {
   };
 } // namespace wavm_host_module
 
+ExecutionResult WavmEngine::execute(
+  evmc_context* context,
+  vector<uint8_t> const& code,
+  vector<uint8_t> const& state_code,
+  evmc_message const& msg,
+  bool meterInterfaceGas
+) {
+  ExecutionResult result = internalExecute(context, code, state_code, msg, meterInterfaceGas);
+  // And clean up mess left by this run.
+  Runtime::collectGarbage();
+  return result;
+}
+
 ExecutionResult WavmEngine::internalExecute(
   evmc_context* context,
   vector<uint8_t> const& code,
diff --git a/src/wavm.h b/src/wavm.h
index cc185cf76..44cfb4ef8 100644
--- a/src/wavm.h
+++ b/src/wavm.h
@@ -17,52 +17,13 @@
 
 #pragma once
 
-#include <iostream>
-#include <memory>
-#include <stack>
-
-#define DLL_IMPORT // Needed by wavm on some platforms
-#include "Inline/Serialization.h"
-#include "IR/Module.h"
-#include "IR/Validate.h"
-#include "Runtime/Intrinsics.h"
-#include "Runtime/Linker.h"
-#include "Runtime/Runtime.h"
-#include "WASM/WASM.h"
-
 #include "eei.h"
 
 namespace hera {
 
-class WavmEthereumInterface : public EthereumInterface {
-
-public:
-  explicit WavmEthereumInterface(
-    evmc_context* _context,
-    std::vector<uint8_t> const& _code,
-    evmc_message const& _msg,
-    ExecutionResult & _result,
-    bool _meterGas
-  ):
-    EthereumInterface(_context, _code, _msg, _result, _meterGas)
-  {}
-
-  void setWasmMemory(Runtime::MemoryInstance* _wasmMemory) {
-    m_wasmMemory = _wasmMemory;
-  }
-
-private:
-  // These assume that m_wasmMemory was set prior to execution.
-  size_t memorySize() const override { return Runtime::getMemoryNumPages(m_wasmMemory) * 65536; }
-  void memorySet(size_t offset, uint8_t value) override { (Runtime::memoryArrayPtr<U8>(m_wasmMemory, offset, 1))[0] = value; }
-  uint8_t memoryGet(size_t offset) override { return (Runtime::memoryArrayPtr<U8>(m_wasmMemory, offset, 1))[0]; }
-
-  Runtime::MemoryInstance* m_wasmMemory;
-};
-
 class WavmEngine : public WasmEngine {
 public:
-  /// Factory method to create the WABT Wasm Engine.
+  /// Factory method to create the WAVM Wasm Engine.
   static std::unique_ptr<WasmEngine> create();
 
   ExecutionResult execute(
@@ -71,12 +32,7 @@ class WavmEngine : public WasmEngine {
     std::vector<uint8_t> const& state_code,
     evmc_message const& msg,
     bool meterInterfaceGas
-  ) override {
-    ExecutionResult result = internalExecute(context, code, state_code, msg, meterInterfaceGas);
-    // And clean up mess left by this run.
-    Runtime::collectGarbage();
-    return result;
-  }
+  ) override;
 
 private:
   ExecutionResult internalExecute(