diff --git a/include/bitcoin/server/define.hpp b/include/bitcoin/server/define.hpp
index 0b8d0ce0..0b2c5e9c 100644
--- a/include/bitcoin/server/define.hpp
+++ b/include/bitcoin/server/define.hpp
@@ -37,9 +37,6 @@
     #define BCS_INTERNAL BC_HELPER_DLL_LOCAL
 #endif
 
-/// Prevent bogus vc++ warnings on protocol.
-BC_DISABLE_WARNING(DIAMOND_INHERITANCE)
-
 /// Augment limited xcode placeholder defines (10 vs. common 20).
 /// ---------------------------------------------------------------------------
 #if defined (HAVE_XCODE)
diff --git a/include/bitcoin/server/interfaces/electrum.hpp b/include/bitcoin/server/interfaces/electrum.hpp
index c262f3b0..ece3ab24 100644
--- a/include/bitcoin/server/interfaces/electrum.hpp
+++ b/include/bitcoin/server/interfaces/electrum.hpp
@@ -32,8 +32,8 @@ struct electrum_methods
     static constexpr std::tuple methods
     {
         /// Blockchain methods.
-        method<"blockchain.block.header", number_t, number_t>{ "height", "cp_height" },
-        method<"blockchain.block.headers", number_t, number_t, number_t>{ "start_height", "count", "cp_height" },
+        method<"blockchain.block.header", number_t, optional<0.0>>{ "height", "cp_height" },
+        method<"blockchain.block.headers", number_t, number_t, optional<0.0>>{ "start_height", "count", "cp_height" },
         method<"blockchain.headers.subscribe">{},
         method<"blockchain.estimatefee", number_t, optional<""_t>>{ "number", "mode" },
         method<"blockchain.relayfee">{},
diff --git a/include/bitcoin/server/protocols/protocol_electrum.hpp b/include/bitcoin/server/protocols/protocol_electrum.hpp
index bae5e85c..238d0562 100644
--- a/include/bitcoin/server/protocols/protocol_electrum.hpp
+++ b/include/bitcoin/server/protocols/protocol_electrum.hpp
@@ -48,8 +48,13 @@ class BCS_API protocol_electrum
     }
 
     void start() NOEXCEPT override;
+    void stopping(const code& ec) NOEXCEPT override;
 
 protected:
+    /// Handlers (event subscription).
+    bool handle_event(const code&, node::chase event_,
+        node::event_value) NOEXCEPT;
+
     /// Handlers (blockchain).
     void handle_blockchain_block_header(const code& ec,
         rpc_interface::blockchain_block_header, double height,
diff --git a/src/protocols/protocol_electrum.cpp b/src/protocols/protocol_electrum.cpp
index 4f6a5907..331d47b5 100644
--- a/src/protocols/protocol_electrum.cpp
+++ b/src/protocols/protocol_electrum.cpp
@@ -47,6 +47,9 @@ void protocol_electrum::start() NOEXCEPT
     if (started())
         return;
 
+    // Events subscription is asynchronous, events may be missed.
+    subscribe_events(BIND(handle_event, _1, _2, _3));
+
     // Blockchain methods.
     SUBSCRIBE_RPC(handle_blockchain_block_header, _1, _2, _3, _4);
     SUBSCRIBE_RPC(handle_blockchain_block_headers, _1, _2, _3, _4, _5);
@@ -78,17 +81,51 @@ void protocol_electrum::start() NOEXCEPT
     protocol_rpc<channel_electrum>::start();
 }
 
+void protocol_electrum::stopping(const code& ec) NOEXCEPT
+{
+    // Unsubscriber race is ok.
+    BC_ASSERT(stranded());
+    unsubscribe_events();
+    protocol_rpc<channel_electrum>::stopping(ec);
+}
+
+// Handlers (event subscription).
+// ----------------------------------------------------------------------------
+
+bool protocol_electrum::handle_event(const code&, node::chase event_,
+    node::event_value) NOEXCEPT
+{
+    // Do not pass ec to stopped as it is not a call status.
+    if (stopped())
+        return false;
+
+    switch (event_)
+    {
+        case node::chase::suspend:
+        {
+            break;
+        }
+        default:
+        {
+            break;
+        }
+    }
+
+    return true;
+}
+
 // Handlers (blockchain).
 // ----------------------------------------------------------------------------
 
+// electrum-protocol.readthedocs.io/en/latest/protocol-basics.html#block-headers
 void protocol_electrum::handle_blockchain_block_header(const code& ec,
-    rpc_interface::blockchain_block_header, double ,
-    double ) NOEXCEPT
+    rpc_interface::blockchain_block_header, double height,
+    double cp_height) NOEXCEPT
 {
-    if (stopped(ec)) return;
-    send_code(error::not_implemented);
+    handle_blockchain_block_headers(ec, {}, height, 1, cp_height);
 }
 
+// electrum-protocol.readthedocs.io/en/latest/protocol-basics.html#block-headers
 void protocol_electrum::handle_blockchain_block_headers(const code& ec,
     rpc_interface::blockchain_block_headers, double ,
     double , double ) NOEXCEPT
@@ -120,6 +157,8 @@ void protocol_electrum::handle_blockchain_headers_subscribe(const code& ec,
     header->to_data(writer);
     BC_ASSERT(writer);
 
+    // TODO: signal header subscription.
+
     // TODO: idempotent subscribe to chase::organized via session/chaser/node.
     // TODO: upon notification send just the header notified by the link.
     // TODO: it is client responsibility to deal with reorgs and race gaps.
@@ -269,6 +308,7 @@ void protocol_electrum::handle_server_features(const code& ec,
     send_code(error::not_implemented);
 }
 
+// This is not actually a subscription method.
 void protocol_electrum::handle_server_peers_subscribe(const code& ec,
     rpc_interface::server_peers_subscribe) NOEXCEPT
 {