diff --git a/src/main/java/org/apache/xmlbeans/impl/richParser/XMLStreamReaderExtImpl.java b/src/main/java/org/apache/xmlbeans/impl/richParser/XMLStreamReaderExtImpl.java
index 6b80189bf..c015a3f0b 100644
--- a/src/main/java/org/apache/xmlbeans/impl/richParser/XMLStreamReaderExtImpl.java
+++ b/src/main/java/org/apache/xmlbeans/impl/richParser/XMLStreamReaderExtImpl.java
@@ -182,11 +182,11 @@ public InputStream getBase64Value()
         throws XMLStreamException, InvalidLexicalValueException {
         _charSeq.reload(CharSeqTrimWS.XMLWHITESPACE_TRIM);
         String text = _charSeq.toString();
-        byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
-        if (buf != null) {
+        try {
+            byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
             return new ByteArrayInputStream(buf);
-        } else {
-            throw new InvalidLexicalValueException("invalid base64Binary value", _charSeq.getLocation());
+        } catch (IllegalArgumentException e) {
+            throw new InvalidLexicalValueException("invalid base64Binary value", e, _charSeq.getLocation());
         }
     }
 
@@ -332,11 +332,11 @@ public InputStream getAttributeHexBinaryValue(int index) throws XMLStreamExcepti
 
     public InputStream getAttributeBase64Value(int index) throws XMLStreamException {
         String text = _charSeq.reloadAtt(index, CharSeqTrimWS.XMLWHITESPACE_TRIM).toString();
-        byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
-        if (buf != null) {
+        try {
+            byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
             return new ByteArrayInputStream(buf);
-        } else {
-            throw new InvalidLexicalValueException("invalid base64Binary value", _charSeq.getLocation());
+        } catch (IllegalArgumentException e) {
+            throw new InvalidLexicalValueException("invalid base64Binary value", e, _charSeq.getLocation());
         }
     }
 
@@ -486,11 +486,11 @@ public InputStream getAttributeHexBinaryValue(String uri, String local) throws X
     public InputStream getAttributeBase64Value(String uri, String local) throws XMLStreamException {
         CharSequence cs = _charSeq.reloadAtt(uri, local, CharSeqTrimWS.XMLWHITESPACE_TRIM);
         String text = cs.toString();
-        byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
-        if (buf != null) {
+        try {
+            byte[] buf = Base64.getMimeDecoder().decode(text.getBytes(StandardCharsets.ISO_8859_1));
             return new ByteArrayInputStream(buf);
-        } else {
-            throw new InvalidLexicalValueException("invalid base64Binary value", _charSeq.getLocation());
+        } catch (IllegalArgumentException e) {
+            throw new InvalidLexicalValueException("invalid base64Binary value", e, _charSeq.getLocation());
         }
     }
 
diff --git a/src/test/java/misc/checkin/RichParserTests.java b/src/test/java/misc/checkin/RichParserTests.java
index 0d9be40c9..f0c1049e5 100755
--- a/src/test/java/misc/checkin/RichParserTests.java
+++ b/src/test/java/misc/checkin/RichParserTests.java
@@ -16,6 +16,7 @@
 package misc.checkin;
 
 import org.apache.xmlbeans.*;
+import org.apache.xmlbeans.impl.common.InvalidLexicalValueException;
 import org.apache.xmlbeans.impl.richParser.XMLStreamReaderExt;
 import org.apache.xmlbeans.impl.richParser.XMLStreamReaderExtImpl;
 import org.junit.jupiter.api.Test;
@@ -36,6 +37,7 @@
 import java.util.Date;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 
 /**
@@ -66,6 +68,34 @@ void testPrimitiveTypes() throws Exception {
         }
     }
 
+    @Test
+    void testInvalidBase64ThrowsInvalidLexicalValue() throws Exception {
+        // "A" is a single base64 char, the MIME decoder rejects it with
+        // IllegalArgumentException. The rich parser must surface that as the
+        // documented InvalidLexicalValueException, like the other getters.
+        XMLStreamReaderExt elem = atFirstStartElement("<a>A</a>");
+        assertThrows(InvalidLexicalValueException.class, elem::getBase64Value);
+
+        XMLStreamReaderExt attByIndex = atFirstStartElement("<a b=\"A\"/>");
+        assertThrows(InvalidLexicalValueException.class, () -> attByIndex.getAttributeBase64Value(0));
+
+        XMLStreamReaderExt attByName = atFirstStartElement("<a b=\"A\"/>");
+        assertThrows(InvalidLexicalValueException.class, () -> attByName.getAttributeBase64Value("", "b"));
+    }
+
+    private static XMLStreamReaderExt atFirstStartElement(String xml) throws Exception {
+        XMLStreamReader xsr = XmlObject.Factory.parse(xml).newXMLStreamReader();
+        XMLStreamReaderExt ext = new XMLStreamReaderExtImpl(xsr);
+        int evt = ext.getEventType();
+        while (evt != XMLEvent.START_ELEMENT && ext.hasNext()) {
+            evt = ext.next();
+        }
+        if (evt != XMLEvent.START_ELEMENT) {
+            throw new IllegalStateException("no start element in: " + xml);
+        }
+        return ext;
+    }
+
     private static final String[] strings = {
         "    this is a long string ... in attribute  ",
         "    this is a long string\n... in text  "};