diff --git a/src/base/similarity_transform.cc b/src/base/similarity_transform.cc
index 9b88fc5a1..19b18df19 100755
--- a/src/base/similarity_transform.cc
+++ b/src/base/similarity_transform.cc
@@ -64,10 +64,11 @@ struct ReconstructionAlignmentEstimator {
                             const std::vector<Y_t>& images2) const {
     CHECK_GE(images1.size(), 3);
     CHECK_GE(images2.size(), 3);
+    CHECK_EQ(images1.size(), images2.size());
 
     std::vector<Eigen::Vector3d> proj_centers1(images1.size());
     std::vector<Eigen::Vector3d> proj_centers2(images2.size());
-    for (size_t i = 0; i < 3; ++i) {
+    for (size_t i = 0; i < images1.size(); ++i) {
       CHECK_EQ(images1[i]->ImageId(), images2[i]->ImageId());
       proj_centers1[i] = images1[i]->ProjectionCenter();
       proj_centers2[i] = images2[i]->ProjectionCenter();