diff --git a/internal/ceres/block_structure.cc b/internal/ceres/block_structure.cc
index 6479b60..39ba082 100644
--- a/internal/ceres/block_structure.cc
+++ b/internal/ceres/block_structure.cc
@@ -35,7 +35,7 @@
 
 bool CellLessThan(const Cell& lhs, const Cell& rhs) {
   if (lhs.block_id == rhs.block_id) {
-    return (lhs.position  < rhs.position);
+    return (lhs.position < rhs.position);
   }
   return (lhs.block_id < rhs.block_id);
 }