diff --git a/src/gpu/VirtualFluids_GPU/DataStructureInitializer/GridReaderFiles/GridReader.cpp b/src/gpu/VirtualFluids_GPU/DataStructureInitializer/GridReaderFiles/GridReader.cpp
index a21c3c8c9f4cf3842ab6bcbf4b040138c0875ede..c322f48b98bb5a8107e83802d161725b71e888bf 100644
--- a/src/gpu/VirtualFluids_GPU/DataStructureInitializer/GridReaderFiles/GridReader.cpp
+++ b/src/gpu/VirtualFluids_GPU/DataStructureInitializer/GridReaderFiles/GridReader.cpp
@@ -632,7 +632,7 @@ void GridReader::initalGridInformations()
     std::vector<int> gridX, gridY, gridZ;
     std::vector<int> distX, distY, distZ;
 
-	for (size_t i = 0; i <= maxLevel; i++) {
+	for (int i = 0; i <= maxLevel; i++) {
         gridX.push_back(0);
         gridY.push_back(0);
         gridZ.push_back(0);