diff --git a/ethminer/MinerAux.h b/ethminer/MinerAux.h
index 964a23635..80886cd7a 100644
--- a/ethminer/MinerAux.h
+++ b/ethminer/MinerAux.h
@@ -553,7 +553,7 @@ private:
 	unsigned m_localWorkSize = ethash_cl_miner::c_defaultLocalWorkSize;
 	unsigned m_msPerBatch = ethash_cl_miner::c_defaultMSPerBatch;
 #endif
-	boost::optional<uint64_t> m_currentBlock;
+	uint64_t m_currentBlock = 0;
 	// default value is 350MB of GPU memory for other stuff (windows system rendering, e.t.c.)
 	unsigned m_extraGPUMemory = 350000000;
 
diff --git a/libethash-cl/ethash_cl_miner.cpp b/libethash-cl/ethash_cl_miner.cpp
index 8e2a7dc4d..942819ba8 100644
--- a/libethash-cl/ethash_cl_miner.cpp
+++ b/libethash-cl/ethash_cl_miner.cpp
@@ -149,7 +149,7 @@ bool ethash_cl_miner::configureGPU(
 	unsigned _msPerBatch,
 	bool _allowCPU,
 	unsigned _extraGPUMemory,
-	boost::optional<uint64_t> _currentBlock
+	uint64_t _currentBlock
 )
 {
 	s_workgroupSize = _localWorkSize;
@@ -158,7 +158,7 @@ bool ethash_cl_miner::configureGPU(
 	s_allowCPU = _allowCPU;
 	s_extraRequiredGPUMem = _extraGPUMemory;
 	// by default let's only consider the DAG of the first epoch
-	uint64_t dagSize = _currentBlock ? ethash_get_datasize(*_currentBlock) : 1073739904U;
+	uint64_t dagSize = ethash_get_datasize(_currentBlock);
 	uint64_t requiredSize =  dagSize + _extraGPUMemory;
 	return searchForAllDevices(_platformId, [&requiredSize](cl::Device const _device) -> bool
 		{
diff --git a/libethash-cl/ethash_cl_miner.h b/libethash-cl/ethash_cl_miner.h
index 094541cf9..fb28dc04b 100644
--- a/libethash-cl/ethash_cl_miner.h
+++ b/libethash-cl/ethash_cl_miner.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#define __CL_ENABLE_EXCEPTIONS 
+#define __CL_ENABLE_EXCEPTIONS
 #define CL_USE_DEPRECATED_OPENCL_2_0_APIS
 
 #if defined(__clang__)
@@ -12,7 +12,6 @@
 #include "cl.hpp"
 #endif
 
-#include <boost/optional.hpp>
 #include <time.h>
 #include <functional>
 #include <libethash/ethash.h>
@@ -50,7 +49,7 @@ public:
 		unsigned _msPerBatch,
 		bool _allowCPU,
 		unsigned _extraGPUMemory,
-		boost::optional<uint64_t> _currentBlock
+		uint64_t _currentBlock
 	);
 
 	bool init(
diff --git a/libethcore/Ethash.cpp b/libethcore/Ethash.cpp
index fc0e07f12..9be76926d 100644
--- a/libethcore/Ethash.cpp
+++ b/libethcore/Ethash.cpp
@@ -416,7 +416,7 @@ bool Ethash::GPUMiner::configureGPU(
 	unsigned _deviceId,
 	bool _allowCPU,
 	unsigned _extraGPUMemory,
-	boost::optional<uint64_t> _currentBlock
+	uint64_t _currentBlock
 )
 {
 	s_platformId = _platformId;
diff --git a/libethcore/Ethash.h b/libethcore/Ethash.h
index e9ddf16ca..7ffd887d0 100644
--- a/libethcore/Ethash.h
+++ b/libethcore/Ethash.h
@@ -88,7 +88,7 @@ public:
 		static unsigned instances() { return s_numInstances > 0 ? s_numInstances : std::thread::hardware_concurrency(); }
 		static std::string platformInfo();
 		static void listDevices() {}
-		static bool configureGPU(unsigned, unsigned, unsigned, unsigned, unsigned, bool, unsigned,  boost::optional<uint64_t>) { return false; }
+		static bool configureGPU(unsigned, unsigned, unsigned, unsigned, unsigned, bool, unsigned, uint64_t) { return false; }
 		static void setNumInstances(unsigned _instances) { s_numInstances = std::min<unsigned>(_instances, std::thread::hardware_concurrency()); }
 	protected:
 		void kickOff() override
@@ -125,7 +125,7 @@ public:
 			unsigned _deviceId,
 			bool _allowCPU,
 			unsigned _extraGPUMemory,
-			boost::optional<uint64_t> _currentBlock
+			uint64_t _currentBlock
 		);
 		static void setNumInstances(unsigned _instances) { s_numInstances = std::min<unsigned>(_instances, getNumDevices()); }