diff --git a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/Ellipse.java b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/Ellipse.java
index 703a24b499..ce63d9fc11 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/Ellipse.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xdgf/usermodel/section/geometry/Ellipse.java
@@ -59,6 +59,11 @@ public class Ellipse implements GeometryRow {
         for (CellType cell : row.getCellArray()) {
             String cellName = cell.getN();
 
+            if (cellName == null) {
+                throw new POIXMLException("Invalid cell '" + cellName
+                        + "' in Ellipse row");
+            }
+
             switch (cellName) {
                 case "X":
                     x = XDGFCell.parseDoubleValue(cell);
diff --git a/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4537225637134336.vsd b/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4537225637134336.vsd
new file mode 100644
index 0000000000..fd033e801f
Binary files /dev/null and b/test-data/diagram/clusterfuzz-testcase-minimized-POIVisioFuzzer-4537225637134336.vsd differ
diff --git a/test-data/spreadsheet/stress.xls b/test-data/spreadsheet/stress.xls
index 7c42429886..9ad1991a26 100644
Binary files a/test-data/spreadsheet/stress.xls and b/test-data/spreadsheet/stress.xls differ