diff --git a/cmd/mrmath.cpp b/cmd/mrmath.cpp
index bdcf5c9aeb..eb899cb9f6 100644
--- a/cmd/mrmath.cpp
+++ b/cmd/mrmath.cpp
@@ -310,7 +310,7 @@ template <class Operation> class ImageKernel : public ImageKernelBase {
 
 protected:
   Voxel2Vector v2v;
-  vector<Operation> data;
+  std::vector<Operation> data;
 };
 
 void run() {