diff --git a/include/ircd/m/id.h b/include/ircd/m/id.h
index c29efe317..538b2612d 100644
--- a/include/ircd/m/id.h
+++ b/include/ircd/m/id.h
@@ -14,6 +14,7 @@
 namespace ircd::m
 {
 	struct id;
+	struct event; // forward declaration for id::event ctors
 
 	IRCD_M_EXCEPTION(error, INVALID_MXID, http::BAD_REQUEST)
 	IRCD_M_EXCEPTION(INVALID_MXID, BAD_SIGIL, http::BAD_REQUEST)
@@ -178,7 +179,7 @@ struct ircd::m::id::event
 struct ircd::m::id::event::v3
 :ircd::m::id::event
 {
-	v3(const mutable_buffer &out, const json::object &);
+	v3(const mutable_buffer &out, const m::event &);
 	v3(const string_view &id);
 	v3() = default;
 };
@@ -187,7 +188,7 @@ struct ircd::m::id::event::v3
 struct ircd::m::id::event::v4
 :ircd::m::id::event
 {
-	v4(const mutable_buffer &out, const json::object &);
+	v4(const mutable_buffer &out, const m::event &);
 	v4(const string_view &id);
 	v4() = default;
 };
diff --git a/ircd/m_id.cc b/ircd/m_id.cc
index 041bd7344..abf79ed98 100644
--- a/ircd/m_id.cc
+++ b/ircd/m_id.cc
@@ -692,7 +692,7 @@ ircd::m::id::event::v3::v3(const string_view &id)
 }
 
 ircd::m::id::event::v3::v3(const mutable_buffer &out,
-                           const json::object &event)
+                           const m::event &event)
 :v3{[&out, event]
 {
 	if(unlikely(buffer::size(out) < 44))
@@ -701,9 +701,21 @@ ircd::m::id::event::v3::v3(const mutable_buffer &out,
 			"Output buffer insufficient for v3 event_id"
 		};
 
+	thread_local char content_buffer[m::event::MAX_SIZE];
+	const m::event essential
+	{
+		m::essential(event, content_buffer)
+	};
+
+	thread_local char preimage_buffer[m::event::MAX_SIZE];
+	const json::object &preimage
+	{
+		json::stringify(preimage_buffer, essential)
+	};
+
 	const sha256::buf hash
 	{
-		sha256{event}
+		sha256{preimage}
 	};
 
 	out[0] = '$';
@@ -735,7 +747,7 @@ ircd::m::id::event::v4::v4(const string_view &id)
 }
 
 ircd::m::id::event::v4::v4(const mutable_buffer &out,
-                           const json::object &event)
+                           const m::event &event)
 :v4{[&out, event]
 {
 	if(unlikely(buffer::size(out) < 44))
@@ -744,9 +756,21 @@ ircd::m::id::event::v4::v4(const mutable_buffer &out,
 			"Output buffer insufficient for v4 event_id"
 		};
 
+	thread_local char content_buffer[m::event::MAX_SIZE];
+	const m::event essential
+	{
+		m::essential(event, content_buffer)
+	};
+
+	thread_local char preimage_buffer[m::event::MAX_SIZE];
+	const json::object &preimage
+	{
+		json::stringify(preimage_buffer, essential)
+	};
+
 	const sha256::buf hash
 	{
-		sha256{event}
+		sha256{preimage}
 	};
 
 	out[0] = '$';