diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 8d6c2eb..5898ec3 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -2307,6 +2307,8 @@ bool checkMaxBetweenExclusiveImpl(Node3 *n, int begin, int end,
   assert(!(begin == -1 && end == 256));
 
   auto *self = static_cast<Node3 *>(n);
+  assume(1 <= self->numChildren);
+  assume(self->numChildren <= 3);
 
   ++begin;