diff --git a/internal/jsonrpc2/conn.go b/internal/jsonrpc2/conn.go
index a47c3d1..2ab8a55 100644
--- a/internal/jsonrpc2/conn.go
+++ b/internal/jsonrpc2/conn.go
@@ -322,8 +322,8 @@ func (c *Connection) readIncoming(ctx context.Context, reader Reader, toQueue ch
 			// cancelled by id
 			if msg.IsCall() {
 				pending := <-c.incomingBox
-				c.incomingBox <- pending
 				pending[msg.ID] = entry
+				c.incomingBox <- pending
 			}
 			// send the message to the incoming queue
 			toQueue <- entry
diff --git a/internal/jsonrpc2/jsonrpc2_test.go b/internal/jsonrpc2/jsonrpc2_test.go
index 5f0674f..15aca11 100644
--- a/internal/jsonrpc2/jsonrpc2_test.go
+++ b/internal/jsonrpc2/jsonrpc2_test.go
@@ -60,6 +60,14 @@ var callTests = []invoker{
 		notify{"unblock", "a"},
 		collect{"a", true, false},
 	}},
+	sequence{"concurrent", []invoker{
+		async{"a", "fork", "a"},
+		notify{"unblock", "a"},
+		async{"b", "fork", "b"},
+		notify{"unblock", "b"},
+		collect{"a", true, false},
+		collect{"b", true, false},
+	}},
 }
 
 type binder struct {