diff --git a/src/trace/opentelemetry_trace.ml b/src/trace/opentelemetry_trace.ml
index 248c8caa..f3484b31 100644
--- a/src/trace/opentelemetry_trace.ml
+++ b/src/trace/opentelemetry_trace.ml
@@ -1,6 +1,8 @@
 open Common_
 
 module Extensions = struct
+  type Otrace.span += Span_otel of OTEL.Span.t
+
   type Otrace.extension_event +=
     | Ev_link_span of Otrace.span * OTEL.Span_ctx.t
     | Ev_record_exn of {
@@ -19,10 +21,6 @@ end
 
 open Extensions
 
-open struct
-  type Otrace.span += Span_otel of OTEL.Span.t
-end
-
 open struct
   type state = {
     clock: Opentelemetry_core.Clock.t;
diff --git a/src/trace/opentelemetry_trace.mli b/src/trace/opentelemetry_trace.mli
index ed421f99..4b590869 100644
--- a/src/trace/opentelemetry_trace.mli
+++ b/src/trace/opentelemetry_trace.mli
@@ -21,6 +21,9 @@ module Otrace := Trace_core
 
 (** The extension events for {!Trace_core}. *)
 module Extensions : sig
+  type Otrace.span +=
+    | Span_otel of OTEL.Span.t  (** The type of span used for OTEL *)
+
   type Otrace.extension_event +=
     | Ev_link_span of Otrace.span * OTEL.Span_ctx.t
           (** Link the given span to the given context. The context isn't the