diff --git a/src/network/connection.c b/src/network/connection.c
index 3de2b09f..6d1e74d6 100644
--- a/src/network/connection.c
+++ b/src/network/connection.c
@@ -327,37 +327,26 @@ update_connection_progress(struct connection *conn)
 	update_progress(conn->progress, conn->received, conn->est_length, conn->from);
 }
 
-/** Progress timer callback for @a conn->progress.  As explained in
- * start_update_progress(), this function must erase the expired timer
- * ID from @a conn->progress->timer.  */
+/** Progress timer callback for @a conn->progress.  */
 static void
 stat_timer(struct connection *conn)
 {
 	update_connection_progress(conn);
-	/* The expired timer ID has now been erased.  */
 	notify_connection_callbacks(conn);
 }
 
-/** Progress timer callback for @a conn->upload_progress.  As explained
- * in start_update_progress(), this function must erase the expired timer
- * ID from @a conn->upload_progress->timer.  */
+/** Progress timer callback for @a conn->upload_progress.  */
 static void
 upload_stat_timer(struct connection *conn)
 {
 	struct http_connection_info *http = conn->info;
 
 	assert(conn->http_upload_progress);
-	if_assert_failed return;
 	assert(http);
-	if_assert_failed {
-		conn->http_upload_progress->timer = TIMER_ID_UNDEF;
-		/* The expired timer ID has now been erased.  */
-		return;
-	}
+	if_assert_failed return;
 
 	update_progress(conn->http_upload_progress, http->post.uploaded,
 		http->post.total_upload_length, http->post.uploaded);
-	/* The expired timer ID has now been erased.  */
 	notify_connection_callbacks(conn);
 }
 
diff --git a/src/network/progress.c b/src/network/progress.c
index 29647649..cf16615e 100644
--- a/src/network/progress.c
+++ b/src/network/progress.c
@@ -45,8 +45,20 @@ done_progress(struct progress *progress)
 	mem_free(progress);
 }
 
-/* Called from the timer callback of @progress->timer.  This function
- * erases the expired timer ID on behalf of the actual callback.  */
+/** Timer callback for progress.timer.  As explained in install_timer(),
+ * this function must erase the expired timer ID from all variables.  */
+static void
+progress_timeout(void *progress_voidptr)
+{
+	struct progress *const progress = progress_voidptr;
+
+	progress->timer = TIMER_ID_UNDEF;
+	/* The expired timer ID has now been erased.  */
+
+	progress->timer_func(progress->timer_func_data);
+}
+
+/* Usually called from the timer callback of @progress->timer.  */
 void
 update_progress(struct progress *progress, off_t loaded, off_t size, off_t pos)
 {
@@ -89,13 +101,14 @@ update_progress(struct progress *progress, off_t loaded, off_t size, off_t pos)
 		timeval_from_seconds(&progress->estimated_time,
 				   (progress->size - progress->pos) / progress->average_speed);
 
-	install_timer(&progress->timer, SPD_DISP_TIME, progress->timer_func, progress->timer_func_data);
-	/* The expired timer ID has now been erased.  */
+	install_timer(&progress->timer, SPD_DISP_TIME,
+		      progress_timeout, progress);
 }
 
-/* As in @install_timer, @timer_func should erase the expired timer ID
- * from @progress->timer.  The usual way to ensure this is to make
- * @timer_func call @update_progress, which sets a new timer.  */
+/*! Unlike in install_timer(), @a timer_func need not erase the
+ * expired timer ID from @a progress->timer.  update_progress()
+ * installs the timer with a wrapper function that takes care of
+ * erasing the timer ID.  */
 void
 start_update_progress(struct progress *progress, void (*timer_func)(void *),
 		      void *timer_func_data)
diff --git a/src/protocol/bittorrent/connection.c b/src/protocol/bittorrent/connection.c
index a57c3736..3416aa23 100644
--- a/src/protocol/bittorrent/connection.c
+++ b/src/protocol/bittorrent/connection.c
@@ -186,9 +186,7 @@ update_bittorrent_connection_state(struct connection *conn)
 	}
 }
 
-/* Progress timer callback for @bittorrent->upload_progress.  As
- * explained in @start_update_progress, this function must erase the
- * expired timer ID from @bittorrent->upload_progress->timer.  */
+/* Progress timer callback for @bittorrent->upload_progress.  */
 static void
 update_bittorrent_connection_upload(void *data)
 {
@@ -198,7 +196,6 @@ update_bittorrent_connection_upload(void *data)
 			bittorrent->uploaded,
 			bittorrent->downloaded,
 			bittorrent->uploaded);
-	/* The expired timer ID has now been erased.  */
 }
 
 void