diff --git a/src/load_layout.c b/src/load_layout.c
index 632c6ec7..7961e17f 100644
--- a/src/load_layout.c
+++ b/src/load_layout.c
@@ -157,6 +157,7 @@ static int json_end_map(void *ctx) {
             }
 
             free(marks);
+            marks = NULL;
             num_marks = 0;
         }
 
diff --git a/testcases/t/267-regress-mark-restart.t b/testcases/t/267-regress-mark-restart.t
index 220d765b..302d23e5 100644
--- a/testcases/t/267-regress-mark-restart.t
+++ b/testcases/t/267-regress-mark-restart.t
@@ -20,6 +20,8 @@ use i3test;
 
 cmd 'open';
 cmd 'mark foo';
+cmd 'open';
+cmd 'mark bar';
 
 cmd 'restart';