diff --git a/core/block_crypt.cpp b/core/block_crypt.cpp
index 7d9a98124..288292a2d 100644
--- a/core/block_crypt.cpp
+++ b/core/block_crypt.cpp
@@ -838,11 +838,11 @@ namespace beam
 		};
 
 		Prehistoric = {
-			// BTC Block #556199
+			// BTC Block #556833
 			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-			0x00, 0x1d, 0x19, 0x8b, 0x75, 0x3d, 0x41, 0x4a,
-			0xce, 0xda, 0x2b, 0x34, 0xec, 0x81, 0x2f, 0x47,
-			0x9b, 0x92, 0x9d, 0x4d, 0xca, 0xc3, 0xd0, 0x3d,
+			0x00, 0x25, 0x2d, 0x12, 0x33, 0xb4, 0x5d, 0xb2,
+			0x39, 0x81, 0x47, 0x67, 0x6e, 0x16, 0x62, 0xf4,
+			0x3c, 0x26, 0xa5, 0x26, 0xd2, 0xe2, 0x20, 0x63,
 		};
 	}
 
diff --git a/core/block_crypt.h b/core/block_crypt.h
index 641499a2b..9cb00ad9c 100644
--- a/core/block_crypt.h
+++ b/core/block_crypt.h
@@ -102,7 +102,7 @@ namespace beam
 			uint32_t MaxAhead_s		= 60 * 15; // 15 minutes. Timestamps ahead by more than 15 minutes won't be accepted
 			uint32_t WindowMedian0	= 25; // Timestamp for a block must be (strictly) higher than the median of preceding window
 			uint32_t WindowMedian1	= 7; // Num of blocks taken at both endings of WindowWork, to pick medians.
-			Difficulty Difficulty0	= Difficulty(8 << Difficulty::s_MantissaBits); // 2^8 = 256
+			Difficulty Difficulty0	= Difficulty(22 << Difficulty::s_MantissaBits); // 2^22 = 4,194,304. For GPUs producing 7 sol/sec this is roughly equivalent to 10K GPUs.
 		} DA;
 
 		struct {