diff --git a/src/tef/writer.ml b/src/tef/writer.ml
index 26286c3..43c920e 100644
--- a/src/tef/writer.ml
+++ b/src/tef/writer.ml
@@ -1,5 +1,3 @@
-open Common_
-
 let char = Buffer.add_char
 let raw_string = Buffer.add_string
 
diff --git a/src/tef/writer.mli b/src/tef/writer.mli
index 536b602..619fa41 100644
--- a/src/tef/writer.mli
+++ b/src/tef/writer.mli
@@ -3,7 +3,6 @@
     This is the part of the code that knows how to emit TEF-compliant JSON from
     raw event data. *)
 
-open Common_
 open Trace_core
 
 val emit_duration_event :