diff --git a/algo/unpack/Unpack.cxx b/algo/unpack/Unpack.cxx
index 7b994ad5f3d05480a77c77b18f3c249f4a9d88da..266e6d1827ceb12e466d4038e1a7bfc36d740c1f 100644
--- a/algo/unpack/Unpack.cxx
+++ b/algo/unpack/Unpack.cxx
@@ -203,9 +203,9 @@ namespace cbm::algo
     xpu::push_timer("Merge");
     xpu::t_add_bytes(nDigisTotal * sizeof(Digi));
     CBM_PARALLEL_FOR(schedule(dynamic))
-    for (unsigned int i = 0; i < numMs; i++) {
-      unsigned int offset = 0;
-      for (unsigned int x = 0; x < i; x++)
+    for (size_t i = 0; i < numMs; i++) {
+      size_t offset = 0;
+      for (size_t x = 0; x < i; x++)
         offset += msDigis[x].size();
       std::copy(msDigis[i].begin(), msDigis[i].end(), digisOut.begin() + offset);
     }