diff --git a/data/Deserializer.h b/data/Deserializer.h
index 2a2d99ea..a51a92a6 100644
--- a/data/Deserializer.h
+++ b/data/Deserializer.h
@@ -94,7 +94,7 @@ namespace cpputils {
         return _readData(size);
     }
 
-    inline Data Deserializer::_readData(uint64_t size) {
+    inline Data Deserializer::_readData(size_t size) {
         Data result(size);
         std::memcpy(static_cast<char*>(result.data()), static_cast<const char*>(_source->dataOffset(_pos)), size);
         _pos += size;
diff --git a/test/data/DataTest.cpp b/test/data/DataTest.cpp
index f3f6ae8c..287313e1 100644
--- a/test/data/DataTest.cpp
+++ b/test/data/DataTest.cpp
@@ -191,12 +191,16 @@ TEST_F(DataTest, Inequality_DifferentLastByte) {
   EXPECT_TRUE(data1 != data2);
 }
 
+#ifdef __x86_64__
 //Needs 64bit for representation. This value isn't in the size param list, because the list is also used for read/write checks.
 TEST_F(DataTest, LargesizeSize) {
-  size_t size = 10L*1024*1024*1024;
+  uint64_t size = 10L*1024*1024*1024;
   Data data(size);
   EXPECT_EQ(size, data.size());
 }
+#else
+#warning This is not a 64bit architecture. Large size data tests are disabled.
+#endif
 
 TEST_F(DataTest, LoadingNonexistingFile) {
   TempFile file(false); // Pass false to constructor, so the tempfile is not created