diff --git a/php/ols.ini b/php/ols.ini
index 6514b83..bc255c4 100644
--- a/php/ols.ini
+++ b/php/ols.ini
@@ -21,3 +21,12 @@ max_input_time = 60
 
 ; Maximum number of input variables that PHP will accept
 max_input_vars = 1000
+
+; Session garbage collection.
+; lsphp ships Debian's php.ini-production, which sets session.gc_probability = 0
+; and delegates cleanup to a sessionclean cron that does not exist in this
+; container. Re-enable PHP's built-in probabilistic GC so stale sess_* files in
+; /var/lib/php/sessions are pruned instead of accumulating indefinitely.
+session.gc_probability = 1
+session.gc_divisor     = 100
+session.gc_maxlifetime = 1440