diff --git a/org/qmckl_sherman_morrison_woodbury.org b/org/qmckl_sherman_morrison_woodbury.org
index 000f06a..d562897 100644
--- a/org/qmckl_sherman_morrison_woodbury.org
+++ b/org/qmckl_sherman_morrison_woodbury.org
@@ -223,13 +223,13 @@ qmckl_exit_code qmckl_sherman_morrison_c(const qmckl_context context,
   double threshold = 0.0;
   qmckl_exit_code rc = qmckl_sherman_morrison_threshold_c(&threshold);
 
-  unsigned int l = 0;
+  uint64_t l = 0;
   // For each update
   while (l < N_updates) {
     // C = A^{-1} x U_l
-    for (unsigned int i = 0; i < Dim; i++) {
+    for (uint64_t i = 0; i < Dim; i++) {
       C[i] = 0;
-      for (unsigned int j = 0; j < Dim; j++) {
+      for (uint64_t j = 0; j < Dim; j++) {
         C[i] += Slater_inv[i * Dim + j] * Updates[l * Dim + j];
       }
     }
@@ -244,13 +244,13 @@ qmckl_exit_code qmckl_sherman_morrison_c(const qmckl_context context,
     double iden = 1 / den;
 
     // D = v^T x A^{-1}
-    for (unsigned int j = 0; j < Dim; j++) {
+    for (uint64_t j = 0; j < Dim; j++) {
       D[j] = Slater_inv[(Updates_index[l] - 1) * Dim + j];
     }
 
     // A^{-1} = A^{-1} - C x D / den
-    for (unsigned int i = 0; i < Dim; i++) {
-      for (unsigned int j = 0; j < Dim; j++) {
+    for (uint64_t i = 0; i < Dim; i++) {
+      for (uint64_t j = 0; j < Dim; j++) {
         double update = C[i] * D[j] * iden;
         Slater_inv[i * Dim + j] -= update;
       }
@@ -415,16 +415,16 @@ qmckl_exit_code qmckl_woodbury_2_c(const qmckl_context context,
 //   std::cerr << "Called Woodbury 2x2 kernel" << std::endl;
 // #endif
 
-  const unsigned int row1 = (Updates_index[0] - 1);
-  const unsigned int row2 = (Updates_index[1] - 1);
+  const uint64_t row1 = (Updates_index[0] - 1);
+  const uint64_t row2 = (Updates_index[1] - 1);
 
   // Compute C = S_inv * U  !! NON-STANDARD MATRIX MULTIPLICATION BECAUSE
   // OF LAYOUT OF 'Updates' !!
   double C[2 * Dim];
-  for (unsigned int i = 0; i < Dim; i++) {
-    for (unsigned int j = 0; j < 2; j++) {
+  for (uint64_t i = 0; i < Dim; i++) {
+    for (uint64_t j = 0; j < 2; j++) {
       C[i * 2 + j] = 0;
-      for (unsigned int k = 0; k < Dim; k++) {
+      for (uint64_t k = 0; k < Dim; k++) {
         C[i * 2 + j] += Slater_inv[i * Dim + k] * Updates[Dim * j + k];
       }
     }
@@ -453,16 +453,16 @@ qmckl_exit_code qmckl_woodbury_2_c(const qmckl_context context,
 
   // Compute tmp = B^{-1} x (V.S^{-1})
   double tmp[2 * Dim];
-  for (unsigned int i = 0; i < 2; i++) {
-    for (unsigned int j = 0; j < Dim; j++) {
+  for (uint64_t i = 0; i < 2; i++) {
+    for (uint64_t j = 0; j < Dim; j++) {
       tmp[i * Dim + j] = Binv[i * 2] * Slater_inv[row1 * Dim + j];
       tmp[i * Dim + j] += Binv[i * 2 + 1] * Slater_inv[row2 * Dim + j];
     }
   }
 
   // Compute (S + U V)^{-1} = S^{-1} - C x tmp
-  for (unsigned int i = 0; i < Dim; i++) {
-    for (unsigned int j = 0; j < Dim; j++) {
+  for (uint64_t i = 0; i < Dim; i++) {
+    for (uint64_t j = 0; j < Dim; j++) {
       Slater_inv[i * Dim + j] -= C[i * 2] * tmp[j];
       Slater_inv[i * Dim + j] -= C[i * 2 + 1] * tmp[Dim + j];
     }