diff --git a/opm/material/common/Tabulated1DFunction.hpp b/opm/material/common/Tabulated1DFunction.hpp
index b217b2922..2af012283 100644
--- a/opm/material/common/Tabulated1DFunction.hpp
+++ b/opm/material/common/Tabulated1DFunction.hpp
@@ -418,7 +418,7 @@ public:
         Scalar x0 = std::min(xi0, xi1);
         Scalar x1 = std::max(xi0, xi1);
         const int n = numSamples() - 1;
-        for (int i = 0; i <= k; ++i) {
+        for (unsigned i = 0; i <= k; ++i) {
             double x = i*(x1 - x0)/k + x0;
             double y;
             double dy_dx;
diff --git a/opm/material/common/UniformXTabulated2DFunction.hpp b/opm/material/common/UniformXTabulated2DFunction.hpp
index cfffb6ea8..59dd3d101 100644
--- a/opm/material/common/UniformXTabulated2DFunction.hpp
+++ b/opm/material/common/UniformXTabulated2DFunction.hpp
@@ -447,7 +447,7 @@ public:
 
         Scalar y0 = 1e30;
         Scalar y1 = -1e30;
-        int n = 0;
+        size_t n = 0;
         for (int i = 0; i < m; ++ i) {
             y0 = std::min(y0, yMin(i));
             y1 = std::max(y1, yMax(i));
@@ -458,7 +458,7 @@ public:
         n *= 3;
         for (int i = 0; i <= m; ++i) {
             Scalar x = x0 + (x1 - x0)*i/m;
-            for (int j = 0; j <= n; ++j) {
+            for (size_t j = 0; j <= n; ++j) {
                 Scalar y = y0 + (y1 - y0)*j/n;
                 os << x << " " << y << " " << eval(x, y) << "\n";
             }