diff --git a/src/Highs.h b/src/Highs.h
index 27c5a936b8..275fa36c3b 100644
--- a/src/Highs.h
+++ b/src/Highs.h
@@ -1515,8 +1515,8 @@ class Highs {
   HighsStatus getRangingInterface();
 
   HighsStatus computeIisInterface();
-  HighsStatus computeInfeasibleRows(const bool elastic_columns = false,
-				    HighsInt* infeasible_row = nullptr);
+  HighsStatus computeInfeasibleRows(const bool elastic_columns,
+				    std::vector<HighsInt>& infeasible_row);
   HighsStatus extractIis(HighsInt& num_iis_col, HighsInt& num_iis_row,
                          HighsInt* iis_col_index, HighsInt* iis_row_index,
                          HighsInt* iis_col_bound, HighsInt* iis_row_bound);
diff --git a/src/lp_data/HighsIis.cpp b/src/lp_data/HighsIis.cpp
index 3a428ed97d..efa989430a 100644
--- a/src/lp_data/HighsIis.cpp
+++ b/src/lp_data/HighsIis.cpp
@@ -150,23 +150,22 @@ bool HighsIis::trivial(const HighsLp& lp, const HighsOptions& options) {
 
 HighsStatus HighsIis::getData(const HighsLp& lp, const HighsOptions& options,
                               const HighsBasis& basis,
-                              const double* dual_ray_value) {
+                              const std::vector<HighsInt>& infeasible_row) {
   // Check for trivial IIS should have been done earlier
   assert(!this->trivial(lp, options));
 
   if (options.iis_strategy == kIisStrategyFromRayRowPriority ||
       options.iis_strategy == kIisStrategyFromRayColPriority) {
     // Identify the LP corresponding to the ray
-    std::vector<HighsInt> from_row;
+    std::vector<HighsInt> from_row = infeasible_row;
     std::vector<HighsInt> from_col;
     std::vector<HighsInt> to_row;
     to_row.assign(lp.num_row_, -1);
     assert(lp.a_matrix_.isColwise());
-    for (HighsInt iRow = 0; iRow < lp.num_row_; iRow++) {
-      if (dual_ray_value[iRow]) {
-        to_row[iRow] = from_row.size();
-        from_row.push_back(iRow);
-      }
+    for (HighsInt iX = 0; iX < HighsInt(infeasible_row.size()); iX++) {
+      HighsInt iRow = infeasible_row[iX];
+      to_row[iRow] = iX;
+      from_row.push_back(iRow);
     }
     for (HighsInt iCol = 0; iCol < lp.num_col_; iCol++) {
       bool use_col = false;
diff --git a/src/lp_data/HighsIis.h b/src/lp_data/HighsIis.h
index f9f418c131..72754c8f0f 100644
--- a/src/lp_data/HighsIis.h
+++ b/src/lp_data/HighsIis.h
@@ -37,7 +37,8 @@ class HighsIis {
   void removeCol(const HighsInt col);
   void removeRow(const HighsInt row);
   HighsStatus getData(const HighsLp& lp, const HighsOptions& options,
-                      const HighsBasis& basis, const double* dual_ray_value);
+                      const HighsBasis& basis,
+		      const std::vector<HighsInt>& infeasible_row);
 
   HighsStatus compute(const HighsLp& lp, const HighsOptions& options,
                       const HighsBasis* basis = nullptr);
diff --git a/src/lp_data/HighsInterface.cpp b/src/lp_data/HighsInterface.cpp
index 7ad4b4d12e..d4f6461581 100644
--- a/src/lp_data/HighsInterface.cpp
+++ b/src/lp_data/HighsInterface.cpp
@@ -1573,7 +1573,7 @@ HighsStatus Highs::computeIisInterface() {
   }
   assert(ekk_instance_.status_.has_invert);
   assert(!lp.is_moved_);
-  std::vector<double> dual_ray_value;
+  std::vector<HighsInt> infeasible_row;
   if (options_.iis_strategy == kIisStrategyFromRayRowPriority ||
       options_.iis_strategy == kIisStrategyFromRayColPriority) {
     const bool has_dual_ray = ekk_instance_.status_.has_dual_ray;
@@ -1582,21 +1582,25 @@ HighsStatus Highs::computeIisInterface() {
       HighsInt iRow = ekk_instance_.info_.dual_ray_row_;
       rhs.assign(num_row, 0);
       rhs[iRow] = ekk_instance_.info_.dual_ray_sign_;
-      dual_ray_value.resize(num_row);
+      std::vector<double> dual_ray_value(num_row);
       HighsInt* dual_ray_num_nz = 0;
       basisSolveInterface(rhs, dual_ray_value.data(), dual_ray_num_nz, NULL,
                           true);
+      for (HighsInt iRow = 0; iRow < lp.num_row_; iRow++) 
+	if (dual_ray_value[iRow]) infeasible_row.push_back(iRow);
     } else {
       highsLogUser(options_.log_options, HighsLogType::kError,
                    "No dual ray to start IIS calculation\n");
       return HighsStatus::kError;
     }
+  } else {
+    this->computeInfeasibleRows(false, infeasible_row);
   }
-  return this->iis_.getData(lp, options_, basis_, dual_ray_value.data());
+  return this->iis_.getData(lp, options_, basis_, infeasible_row);
 }
 
 HighsStatus Highs::computeInfeasibleRows(const bool elastic_columns,
-					 HighsInt* infeasible_row) {
+					 std::vector<HighsInt>& infeasible_row) {
   // Elasticity filter
   //
   // Construct the e-LP: