diff --git a/dumux/io/rasterimagereader.hh b/dumux/io/rasterimagereader.hh
index 4ead3192f7a2ebbed232fee6396bdcced365605b..0e5304f9d633b45fb0325b0102b4bda89f172c31 100644
--- a/dumux/io/rasterimagereader.hh
+++ b/dumux/io/rasterimagereader.hh
@@ -328,7 +328,7 @@ public:
 
         std::size_t rowIdx = 0;
         std::size_t colIdx = 0;
-        for (const auto& val : result)
+        for (const auto val : result)
         {
             image[rowIdx][colIdx] = val;
 
@@ -354,7 +354,7 @@ public:
         std::vector<OutputValueType> data;
         data.reserve(image.size()*image[0].size());
         for (const auto& row: image)
-            for (const auto& col : row)
+            for (const auto col : row)
                 data.push_back(col);
 
         return data;
diff --git a/test/io/rasterimagereader/test_rasterimagereader.cc b/test/io/rasterimagereader/test_rasterimagereader.cc
index 491a4fab09ea6e18cfe7ea19315121b5f60fbba3..3853f420e7e4e84b62dd0bc2de02e680973cb668 100644
--- a/test/io/rasterimagereader/test_rasterimagereader.cc
+++ b/test/io/rasterimagereader/test_rasterimagereader.cc
@@ -49,7 +49,7 @@ int main(int argc, char** argv)
     // print the image
     for (const auto& row: printableBlackAndWhiteImage)
     {
-        for (const auto& col : row)
+        for (bool col : row)
             std::cout << col << " ";
         std::cout << std::endl;
     }
@@ -131,7 +131,7 @@ int main(int argc, char** argv)
     // print the image
     for (const auto& row: printableGrayScaleImage)
     {
-        for (const auto& col : row)
+        for (bool col : row)
             std::cout << std::setw(3) << +col << " ";
         std::cout << std::endl;
     }