diff --git a/src/main/java/org/awdevelopment/smithlab/io/input/XlsxHeaderReader.java b/src/main/java/org/awdevelopment/smithlab/io/input/XlsxHeaderReader.java
index 8a7e1fd..d171a19 100644
--- a/src/main/java/org/awdevelopment/smithlab/io/input/XlsxHeaderReader.java
+++ b/src/main/java/org/awdevelopment/smithlab/io/input/XlsxHeaderReader.java
@@ -16,6 +16,10 @@ public static Headers readHeaders(LoggerHelper LOGGER, XSSFSheet sheet) throws I
         int rowZeroWidth = sheet.getRow(0).getLastCellNum();
         for (int i = 0; i < rowZeroWidth; i++) {
             XSSFCell cell = sheet.getRow(0).getCell(i);
+            if (cell == null) {
+                LOGGER.atWarn("Cell in header row at zero-indexed column "+i+" is null, skipping...");
+                continue;
+            }
             CellType cellType = cell.getCellType();
             if (cellType == CellType._NONE || cellType == CellType.BLANK || cellType == CellType.ERROR) {
                 LOGGER.atWarn("Cell in header row at zero-indexed column "+i
diff --git a/src/main/java/org/awdevelopment/smithlab/io/input/XlsxInputReader.java b/src/main/java/org/awdevelopment/smithlab/io/input/XlsxInputReader.java
index b1800a6..43878ec 100644
--- a/src/main/java/org/awdevelopment/smithlab/io/input/XlsxInputReader.java
+++ b/src/main/java/org/awdevelopment/smithlab/io/input/XlsxInputReader.java
@@ -253,7 +253,27 @@ private Condition readCondition(XSSFCell cell) throws InvalidConditionValueExcep
         }
     }
 
+    private boolean isCellInMergedRegion(XSSFCell cell) {
+        XSSFSheet sheet = cell.getSheet();
+        int rowIndex = cell.getRowIndex();
+        int colIndex = cell.getColumnIndex();
+        return sheet.getMergedRegions().stream().anyMatch(region -> region.isInRange(rowIndex, colIndex));
+    }
+
     private Strain readStrain(XSSFCell cell, Condition condition) throws InvalidStrainValueException {
+        int rowIndex = cell.getRowIndex();
+        int colIndex = cell.getColumnIndex();
+        // Check if the cell is in a merged region
+        if (cell == null || isCellInMergedRegion(cell)) {
+            while (cell == null || cell.getCellType() == CellType.BLANK || cell.getCellType() == CellType.ERROR) {
+                if (rowIndex == 0) break;
+                rowIndex--;
+                cell = cell.getSheet().getRow(rowIndex).getCell(colIndex);
+                rowIndex = cell.getRowIndex();
+                colIndex = cell.getColumnIndex();
+            }
+        }
+
         CellType cellType = cell.getCellType();
         if (cellType == CellType.STRING) {
             String cellContent = cell.getStringCellValue();
@@ -265,8 +285,6 @@ private Strain readStrain(XSSFCell cell, Condition condition) throws InvalidStra
             strains.add(newStrain);
             return newStrain;
         } else if (cellType == CellType.BLANK || cellType == CellType._NONE) {
-            int rowIndex = cell.getRowIndex();
-            int colIndex = cell.getColumnIndex();
             for (int i = rowIndex - 1; i > 1; i--) {
                 XSSFCell nextCell = cell.getSheet().getRow(i).getCell(colIndex);
                 if (nextCell.getCellType() == CellType.STRING) return readStrain(nextCell, condition);