diff --git a/internal/ceres/parameter_block_test.cc b/internal/ceres/parameter_block_test.cc
index 5a2db3c..f01e0ad 100644
--- a/internal/ceres/parameter_block_test.cc
+++ b/internal/ceres/parameter_block_test.cc
@@ -41,7 +41,7 @@
   ParameterBlock parameter_block(x, 3, -1);
 
   // The indices to set constant within the parameter block (used later).
-  vector<int> indices;
+  std::vector<int> indices;
   indices.push_back(1);
 
   // Can't set the parameterization if the sizes don't match.