diff --git a/tests/test_lapack.cpp b/tests/test_lapack.cpp
index 3f5aff91..56b0bbb9 100644
--- a/tests/test_lapack.cpp
+++ b/tests/test_lapack.cpp
@@ -24,34 +24,36 @@
 namespace {
     struct BandMatrixCoeff
     {
-        BandMatrixCoeff(int N, int ku, int kl) : ku_(ku), kl_(kl), nrow_(2*kl + ku + 1), N_(N) {
+        BandMatrixCoeff(MAT_SIZE_T N, MAT_SIZE_T ku, MAT_SIZE_T kl)
+            : ku_(ku), kl_(kl), nrow_(2 * kl + ku + 1), N_(N)
+        {
         }
 
 
         // compute the position where to store the coefficient of a matrix A_{i,j} (i,j=0,...,N-1)
         // in a array which is sent to the band matrix solver of LAPACK.
 
-        int operator ()(int i, int j) {
+        int operator ()(MAT_SIZE_T i, MAT_SIZE_T j) {
             return kl_ + ku_ + i - j + j*nrow_;
         }
 
-        const int ku_;
-        const int kl_;
-        const int nrow_;
-        const int N_;
+        const MAT_SIZE_T ku_;
+        const MAT_SIZE_T kl_;
+        const MAT_SIZE_T nrow_;
+        const MAT_SIZE_T N_;
     };
 } //end anonymous namespace
 
 int main()
 {
-    const int N = 5;
-    const int nrhs = 1;
+    const MAT_SIZE_T N = 5;
+    const MAT_SIZE_T nrhs = 1;
     double DU[N-1] = { 2.1,  -1.0,   1.9,   8.0 };
     double D[N]    = { 3.0,   2.3,  -5.0,  -0.9,   7.1 };
     double DL[N-1] = { 3.4,   3.6,   7.0,  -6.0 };
     double B[N] = { 2.7,  -0.5,   2.6,   0.6,   2.7 };
     // double B[N]    = { 2.7,  -0.5,   2.6,   0.6,   2.7 };
-    int info = 0;
+    MAT_SIZE_T info = 0;
     dgtsv_(&N, &nrhs, DL, D, DU, B, &N, &info);
     if (info == 0) {
         for (int i = 0; i < N; ++i) {
@@ -64,12 +66,12 @@ int main()
     std::cout << std::endl;
 
     //test of dgbsv_
-    int ldb = N;
-    int lda = N;
-    std::vector<int> ipiv(N, 0);
+    MAT_SIZE_T ldb = N;
+    MAT_SIZE_T lda = N;
+    std::vector<MAT_SIZE_T> ipiv(N, 0);
     std::vector<double> AA(N*N, 0.);
     std::vector<double> BB(N, 0.);
-    for (int i = 0; i < N; ++i) {
+    for (MAT_SIZE_T i = 0; i < N; ++i) {
         AA[i + i*N] = 10.;
         if (i > 0) {
             AA[i + (i - 1)*N] = i;
@@ -78,31 +80,31 @@ int main()
         BB[i] = i;
     }
 
-    for (int i = 0; i < N; ++i) {
-        for (int j = 0; j < N; ++j) {
+    for (MAT_SIZE_T i = 0; i < N; ++i) {
+        for (MAT_SIZE_T j = 0; j < N; ++j) {
             std::cout << " " << AA[i + j*N];
         }
         std::cout << " " << std::endl;
     }
     std::cout << std::endl;
 
-    int kl = 1;
-    int ku = 1;
-    int nrowAB = 2*kl + ku + 1;
-    int ldab = nrowAB;
+    MAT_SIZE_T kl = 1;
+    MAT_SIZE_T ku = 1;
+    MAT_SIZE_T nrowAB = 2*kl + ku + 1;
+    MAT_SIZE_T ldab = nrowAB;
     std::vector<double> AB(nrowAB*N, 0.);
     BandMatrixCoeff bmc(N, ku, kl);
 
     // Rewrite AA matrix in band format AB 
-    for (int i = 0; i < N; ++i) {
-        for (int j = -1; j < 2; ++j) {
+    for (MAT_SIZE_T i = 0; i < N; ++i) {
+        for (MAT_SIZE_T j = -1; j < 2; ++j) {
             if (i + j > -1 && i + j < N)
                 AB[bmc(i, i + j)] = AA[i + N*(i + j)];
         }
     }
 
-    for (int i = 0; i < nrowAB; ++i) {
-        for (int j = 0; j < N; ++j) {
+    for (MAT_SIZE_T i = 0; i < nrowAB; ++i) {
+        for (MAT_SIZE_T j = 0; j < N; ++j) {
             std::cout << " " << AB[i + j*nrowAB];
         }
         std::cout << " " << std::endl;
@@ -113,7 +115,7 @@ int main()
     dgesv_(&N ,&nrhs, &AA[0], &lda, &ipiv[0], &BB[0], &ldb, &info);
 
     if (info == 0) {
-	for (int i = 0; i < N; ++i) {
+	for (MAT_SIZE_T i = 0; i < N; ++i) {
 	    std::cout << BB[i] << ' ';
 	}
 	std::cout << std::endl;
@@ -121,14 +123,14 @@ int main()
 	std::cerr << "Something went wrong in debsv_()\n";
     }
 
-    for (int i = 0; i < N; ++i) {
+    for (MAT_SIZE_T i = 0; i < N; ++i) {
         BB[i] = i;
     }
 
     dgbsv_(&N, &kl, &ku, &nrhs, &AB[0], &ldab, &ipiv[0], &BB[0], &ldb, &info);
 
     if (info == 0) {
-        for (int i = 0; i < N; ++i) {
+        for (MAT_SIZE_T i = 0; i < N; ++i) {
             std::cout << BB[i] << ' ';
         }
         std::cout << std::endl;