diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFChartSheet.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFChartSheet.java
index b9944a58d94..798cd4df7b6 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFChartSheet.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFChartSheet.java
@@ -90,8 +90,9 @@ protected void write(OutputStream out) throws IOException {
         XmlOptions xmlOptions = new XmlOptions(DEFAULT_XML_OPTIONS);
         xmlOptions.setSaveSyntheticDocumentElement(
                 new QName(CTChartsheet.type.getName().getNamespaceURI(), "chartsheet"));
-        chartsheet.save(out, xmlOptions);
-
+        if (chartsheet != null) {
+            chartsheet.save(out, xmlOptions);
+        }
     }
 
     private static byte[] blankWorksheet(){
diff --git a/poi-ooxml/src/test/java/org/apache/poi/ss/tests/TestWorkbookFactory.java b/poi-ooxml/src/test/java/org/apache/poi/ss/tests/TestWorkbookFactory.java
index 200407e3efa..b306dc7712a 100644
--- a/poi-ooxml/src/test/java/org/apache/poi/ss/tests/TestWorkbookFactory.java
+++ b/poi-ooxml/src/test/java/org/apache/poi/ss/tests/TestWorkbookFactory.java
@@ -351,4 +351,12 @@ private boolean openHSSFFile() {
             return false;
         }
     }
+
+    @Test
+    void testEncryptionNullPointerException() throws IOException {
+        assertThrows(IllegalArgumentException.class,
+                () -> WorkbookFactory.create(POIDataSamples.getSpreadSheetInstance().
+                        openResourceAsStream(
+                                "crash-9bf3cd4bd6f50a8a9339d363c2c7af14b536865c.xlsx")));
+    }
 }
diff --git a/poi/src/main/java/org/apache/poi/poifs/crypt/CryptoFunctions.java b/poi/src/main/java/org/apache/poi/poifs/crypt/CryptoFunctions.java
index 587d72eca6c..9a911656604 100644
--- a/poi/src/main/java/org/apache/poi/poifs/crypt/CryptoFunctions.java
+++ b/poi/src/main/java/org/apache/poi/poifs/crypt/CryptoFunctions.java
@@ -252,9 +252,15 @@ public static Cipher getCipher(Key key, CipherAlgorithm cipherAlgorithm, Chainin
             if (cipherAlgorithm == CipherAlgorithm.rc4) {
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId);
             } else if (cipherAlgorithm.needsBouncyCastle) {
+                if (chain == null) {
+                    throw new IllegalArgumentException("Did not have a chain for cipher " + cipherAlgorithm);
+                }
                 registerBouncyCastle();
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId + "/" + chain.jceId + "/" + padding, "BC");
             } else {
+                if (chain == null) {
+                    throw new IllegalArgumentException("Did not have a chain for cipher " + cipherAlgorithm);
+                }
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId + "/" + chain.jceId + "/" + padding);
             }
 
diff --git a/test-data/spreadsheet/crash-274d6342e4842d61be0fb48eaadad6208ae767ae.xlsx b/test-data/spreadsheet/crash-274d6342e4842d61be0fb48eaadad6208ae767ae.xlsx
new file mode 100644
index 00000000000..0707db6706b
Binary files /dev/null and b/test-data/spreadsheet/crash-274d6342e4842d61be0fb48eaadad6208ae767ae.xlsx differ
diff --git a/test-data/spreadsheet/crash-9bf3cd4bd6f50a8a9339d363c2c7af14b536865c.xlsx b/test-data/spreadsheet/crash-9bf3cd4bd6f50a8a9339d363c2c7af14b536865c.xlsx
new file mode 100644
index 00000000000..5c9421f6280
Binary files /dev/null and b/test-data/spreadsheet/crash-9bf3cd4bd6f50a8a9339d363c2c7af14b536865c.xlsx differ
diff --git a/test-data/spreadsheet/stress.xls b/test-data/spreadsheet/stress.xls
index 4436b980e08..fb15d8174a4 100644
Binary files a/test-data/spreadsheet/stress.xls and b/test-data/spreadsheet/stress.xls differ