diff --git a/c/segment.c b/c/segment.c
index a5b333558d..cef05b75de 100644
--- a/c/segment.c
+++ b/c/segment.c
@@ -240,9 +240,12 @@ static void initialize_seginfo(seginfo *si, ISPC s, IGEN g) {
   si->trigger_guardians = 0;
   si->locked_objects = Snil;
   si->unlocked_objects = Snil;
+  si->locked_mask = NULL;
 #ifdef PRESERVE_FLONUM_EQ
   si->forwarded_flonums = NULL;
 #endif
+  si->counting_mask = NULL;
+  si->measured_mask = NULL;
 }
 
 iptr S_find_segments(s, g, n) ISPC s; IGEN g; iptr n; {