diff --git a/src/storm/builder/ExplicitModelBuilder.cpp b/src/storm/builder/ExplicitModelBuilder.cpp
index e0307344f..6467793c6 100644
--- a/src/storm/builder/ExplicitModelBuilder.cpp
+++ b/src/storm/builder/ExplicitModelBuilder.cpp
@@ -309,7 +309,7 @@ namespace storm {
             buildMatrices(transitionMatrixBuilder, rewardModelBuilders, choiceInformationBuilder, markovianStates);
             
             // Initialize the model components with the obtained information.
-            storm::storage::sparse::ModelComponents<ValueType, RewardModelType> modelComponents(transitionMatrixBuilder.build(0, transitionMatrixBuilder.getLastRowGroup()), buildStateLabeling(), std::unordered_map<std::string, RewardModelType>(), !generator->isDiscreteTimeModel(), std::move(markovianStates));
+            storm::storage::sparse::ModelComponents<ValueType, RewardModelType> modelComponents(transitionMatrixBuilder.build(0, transitionMatrixBuilder.getCurrentRowGroupCount()), buildStateLabeling(), std::unordered_map<std::string, RewardModelType>(), !generator->isDiscreteTimeModel(), std::move(markovianStates));
                         
             // Now finalize all reward models.
             for (auto& rewardModelBuilder : rewardModelBuilders) {
diff --git a/src/storm/storage/SparseMatrix.cpp b/src/storm/storage/SparseMatrix.cpp
index 009e5ab0b..36dd5724e 100644
--- a/src/storm/storage/SparseMatrix.cpp
+++ b/src/storm/storage/SparseMatrix.cpp
@@ -87,7 +87,7 @@ namespace storm {
         }
         
         template<typename ValueType>
-        SparseMatrixBuilder<ValueType>::SparseMatrixBuilder(index_type rows, index_type columns, index_type entries, bool forceDimensions, bool hasCustomRowGrouping, index_type rowGroups) : initialRowCountSet(rows != 0), initialRowCount(rows), initialColumnCountSet(columns != 0), initialColumnCount(columns), initialEntryCountSet(entries != 0), initialEntryCount(entries), forceInitialDimensions(forceDimensions), hasCustomRowGrouping(hasCustomRowGrouping), initialRowGroupCountSet(rowGroups != 0), initialRowGroupCount(rowGroups), rowGroupIndices(), columnsAndValues(), rowIndications(), currentEntryCount(0), lastRow(0), lastColumn(0), highestColumn(0), currentRowGroup(0) {
+        SparseMatrixBuilder<ValueType>::SparseMatrixBuilder(index_type rows, index_type columns, index_type entries, bool forceDimensions, bool hasCustomRowGrouping, index_type rowGroups) : initialRowCountSet(rows != 0), initialRowCount(rows), initialColumnCountSet(columns != 0), initialColumnCount(columns), initialEntryCountSet(entries != 0), initialEntryCount(entries), forceInitialDimensions(forceDimensions), hasCustomRowGrouping(hasCustomRowGrouping), initialRowGroupCountSet(rowGroups != 0), initialRowGroupCount(rowGroups), rowGroupIndices(), columnsAndValues(), rowIndications(), currentEntryCount(0), lastRow(0), lastColumn(0), highestColumn(0), currentRowGroupCount(0) {
             // Prepare the internal storage.
             if (initialRowCountSet) {
                 rowIndications.reserve(initialRowCount + 1);
@@ -105,7 +105,7 @@ namespace storm {
         }
         
         template<typename ValueType>
-        SparseMatrixBuilder<ValueType>::SparseMatrixBuilder(SparseMatrix<ValueType>&& matrix) :  initialRowCountSet(false), initialRowCount(0), initialColumnCountSet(false), initialColumnCount(0), initialEntryCountSet(false), initialEntryCount(0), forceInitialDimensions(false), hasCustomRowGrouping(!matrix.trivialRowGrouping), initialRowGroupCountSet(false), initialRowGroupCount(0), rowGroupIndices(), columnsAndValues(std::move(matrix.columnsAndValues)), rowIndications(std::move(matrix.rowIndications)), currentEntryCount(matrix.entryCount), currentRowGroup() {
+        SparseMatrixBuilder<ValueType>::SparseMatrixBuilder(SparseMatrix<ValueType>&& matrix) :  initialRowCountSet(false), initialRowCount(0), initialColumnCountSet(false), initialColumnCount(0), initialEntryCountSet(false), initialEntryCount(0), forceInitialDimensions(false), hasCustomRowGrouping(!matrix.trivialRowGrouping), initialRowGroupCountSet(false), initialRowGroupCount(0), rowGroupIndices(), columnsAndValues(std::move(matrix.columnsAndValues)), rowIndications(std::move(matrix.rowIndications)), currentEntryCount(matrix.entryCount), currentRowGroupCount() {
             
             lastRow = matrix.rowCount == 0 ? 0 : matrix.rowCount - 1;
             lastColumn = columnsAndValues.empty() ? 0 : columnsAndValues.back().getColumn();
@@ -117,7 +117,7 @@ namespace storm {
                 if (!rowGroupIndices->empty()) {
                     rowGroupIndices.get().pop_back();
                 }
-                currentRowGroup = rowGroupIndices->empty() ? 0 : rowGroupIndices.get().size() - 1;
+                currentRowGroupCount = rowGroupIndices->empty() ? 0 : rowGroupIndices.get().size() - 1;
             }
             
             // Likewise, we need to 'open' the row indications again.
@@ -191,7 +191,7 @@ namespace storm {
             STORM_LOG_THROW(hasCustomRowGrouping, storm::exceptions::InvalidStateException, "Matrix was not created to have a custom row grouping.");
             STORM_LOG_THROW(startingRow >= lastRow, storm::exceptions::InvalidStateException, "Illegal row group with negative size.");
             rowGroupIndices.get().push_back(startingRow);
-            ++currentRowGroup;
+            ++currentRowGroupCount;
             
             // Close all rows from the most recent one to the starting row.
             for (index_type i = lastRow + 1; i < startingRow; ++i) {
@@ -252,14 +252,14 @@ namespace storm {
             
             // Check whether row groups are missing some entries.
             if (hasCustomRowGrouping) {
-                uint_fast64_t rowGroupCount = currentRowGroup;
+                uint_fast64_t rowGroupCount = currentRowGroupCount;
                 if (initialRowGroupCountSet && forceInitialDimensions) {
                     STORM_LOG_THROW(rowGroupCount <= initialRowGroupCount, storm::exceptions::InvalidStateException, "Expected not more than " << initialRowGroupCount << " row groups, but got " << rowGroupCount << ".");
                     rowGroupCount = std::max(rowGroupCount, initialRowGroupCount);
                 }
                 rowGroupCount = std::max(rowGroupCount, overriddenRowGroupCount);
                 
-                for (index_type i = currentRowGroup; i <= rowGroupCount; ++i) {
+                for (index_type i = currentRowGroupCount; i <= rowGroupCount; ++i) {
                     rowGroupIndices.get().push_back(rowCount);
                 }
             }
@@ -273,11 +273,11 @@ namespace storm {
         }
 
         template<typename ValueType>
-        typename SparseMatrixBuilder<ValueType>::index_type SparseMatrixBuilder<ValueType>::getLastRowGroup() const {
+        typename SparseMatrixBuilder<ValueType>::index_type SparseMatrixBuilder<ValueType>::getCurrentRowGroupCount() const {
             if (this->hasCustomRowGrouping) {
-                return currentRowGroup;
+                return currentRowGroupCount;
             } else {
-                return getLastRow();
+                return getLastRow() + 1;
             }
         }
 
diff --git a/src/storm/storage/SparseMatrix.h b/src/storm/storage/SparseMatrix.h
index 98eb959b5..e07389e5a 100644
--- a/src/storm/storage/SparseMatrix.h
+++ b/src/storm/storage/SparseMatrix.h
@@ -220,11 +220,11 @@ namespace storm {
             index_type getLastRow() const;
 
             /*!
-             * Retrieves the most recently used row group.
+             * Retrieves the current row group count.
              *
-             * @return The most recently used row group.
+             * @return The current row group count.
              */
-            index_type getLastRowGroup() const;
+            index_type getCurrentRowGroupCount() const;
 
             /*!
              * Retrieves the most recently used row.
@@ -303,7 +303,7 @@ namespace storm {
             
             // Stores the currently active row group. This is used for correctly constructing the row grouping of the
             // matrix.
-            index_type currentRowGroup;
+            index_type currentRowGroupCount;
         };
         
         /*!