diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 495da63..b05d105 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -766,6 +766,8 @@ private:
 
 int getNodeIndex(Node3 *self, uint8_t index) {
   Node3 *n = (Node3 *)self;
+  assume(n->numChildren >= 1);
+  assume(n->numChildren <= 3);
   for (int i = 0; i < n->numChildren; ++i) {
     if (n->index[i] == index) {
       return i;
@@ -1070,6 +1072,8 @@ ChildAndMaxVersion getChildAndMaxVersion(Node *self, uint8_t index) {
 Node *getChildGeq(Node0 *, int) { return nullptr; }
 
 Node *getChildGeq(Node3 *n, int child) {
+  assume(n->numChildren >= 1);
+  assume(n->numChildren <= 3);
   for (int i = 0; i < n->numChildren; ++i) {
     if (n->index[i] >= child) {
       return n->children[i];