diff --git a/tools/crc.cpp b/tools/crc.cpp
index e8083eb..d6f59ef 100644
--- a/tools/crc.cpp
+++ b/tools/crc.cpp
@@ -15,9 +15,9 @@
     const int kExtraRounds = 2;
     const std::uint8_t* bytes = data.data();
     std::uint16_t crc = 0xFFFF;
-    size_t i;
-    size_t j;
-    size_t size = data.size();
+    std::size_t i;
+    std::size_t j;
+    std::size_t size = data.size();
 
     for (i = 0; i < size + kExtraRounds; ++i)
     {