diff --git a/pyevmasm/__main__.py b/pyevmasm/__main__.py
index 3745460..29b29a6 100755
--- a/pyevmasm/__main__.py
+++ b/pyevmasm/__main__.py
@@ -33,8 +33,8 @@ def main():
         "--fork",
         default=DEFAULT_FORK,
         type=str,
-        help="Fork, default: byzantium. "
-        "Possible: frontier, homestead, tangerine_whistle, spurious_dragon, byzantium, constantinople, serenity. "
+        help="Fork, default: london. "
+        "Possible: frontier, homestead, tangerine_whistle, spurious_dragon, byzantium, constantinople, istanbul, london, serenity. "
         "Also an unsigned block number is accepted to select the fork.",
     )
 
diff --git a/pyevmasm/evmasm.py b/pyevmasm/evmasm.py
index 7c87cc0..8d94128 100644
--- a/pyevmasm/evmasm.py
+++ b/pyevmasm/evmasm.py
@@ -1041,8 +1041,9 @@ def block_to_fork(block_number):
         4370000: "byzantium",
         # 7280000: "constantinople", # Same Block as petersburg, commented to avoid conflicts
         7280000: "petersburg",
-        9999999: "serenity",  # to be replaced after Serenity launch
-        12965000: "london"
+        9069000: "istanbul",
+        12965000: "london",
+        99999999: "serenity"  # to be replaced after Serenity launch
     }
     fork_names = list(forks_by_block.values())
     fork_blocks = list(forks_by_block.keys())