diff --git a/HeterogeneousCore/CUDAUtilities/interface/deviceAllocatorStatus.h b/HeterogeneousCore/CUDAUtilities/interface/deviceAllocatorStatus.h
index 92f9f87e890ac..ad335cb7f7fad 100644
--- a/HeterogeneousCore/CUDAUtilities/interface/deviceAllocatorStatus.h
+++ b/HeterogeneousCore/CUDAUtilities/interface/deviceAllocatorStatus.h
@@ -1,15 +1,17 @@
 #ifndef HeterogeneousCore_CUDAUtilities_deviceAllocatorStatus_h
 #define HeterogeneousCore_CUDAUtilities_deviceAllocatorStatus_h
 
+#include <cstddef>
 #include <map>
 
 namespace cms {
   namespace cuda {
     namespace allocator {
       struct TotalBytes {
-        size_t free;
-        size_t live;
-        size_t liveRequested;  // CMS: monitor also requested amount
+        // CMS: add explicit std namespace
+        std::size_t free;
+        std::size_t live;
+        std::size_t liveRequested;  // CMS: monitor also requested amount
         TotalBytes() { free = live = liveRequested = 0; }
       };
       /// Map type of device ordinals to the number of cached bytes cached by each device