diff --git a/src/main/java/org/apache/xmlbeans/impl/store/Saver.java b/src/main/java/org/apache/xmlbeans/impl/store/Saver.java
index 30307954e..bc842c223 100755
--- a/src/main/java/org/apache/xmlbeans/impl/store/Saver.java
+++ b/src/main/java/org/apache/xmlbeans/impl/store/Saver.java
@@ -2070,8 +2070,8 @@ protected void emitPiText(SaveCur c) {
             int off = c._offSrc;
             int index = 0;
             while (index < cch) {
-                int indexLimit = index + 512 > cch ? cch : 512;
-                CharUtil.getChars(_buf, 0, src, off + index, indexLimit);
+                int indexLimit = Math.min(index + 512, cch);
+                CharUtil.getChars(_buf, 0, src, off + index, indexLimit - index);
                 entitizeAndWritePIText(indexLimit - index);
                 index = indexLimit;
             }
@@ -2085,8 +2085,8 @@ protected void emitCommentText(SaveCur c) {
             int off = c._offSrc;
             int index = 0;
             while (index < cch) {
-                int indexLimit = index + 512 > cch ? cch : 512;
-                CharUtil.getChars(_buf, 0, src, off + index, indexLimit);
+                int indexLimit = Math.min(index + 512, cch);
+                CharUtil.getChars(_buf, 0, src, off + index, indexLimit - index);
                 entitizeAndWriteCommentText(indexLimit - index);
                 index = indexLimit;
             }
diff --git a/src/test/java/misc/checkin/SaveOptimizeForSpeedTest.java b/src/test/java/misc/checkin/SaveOptimizeForSpeedTest.java
new file mode 100644
index 000000000..308221bf6
--- /dev/null
+++ b/src/test/java/misc/checkin/SaveOptimizeForSpeedTest.java
@@ -0,0 +1,66 @@
+/*   Copyright 2004 The Apache Software Foundation
+ *
+ *   Licensed under the Apache License, Version 2.0 (the "License");
+ *   you may not use this file except in compliance with the License.
+ *   You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   Unless required by applicable law or agreed to in writing, software
+ *   distributed under the License is distributed on an "AS IS" BASIS,
+ *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *   See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package misc.checkin;
+
+import org.apache.xmlbeans.XmlObject;
+import org.apache.xmlbeans.XmlOptions;
+import org.junit.jupiter.api.Test;
+
+import java.io.StringWriter;
+import java.time.Duration;
+import java.util.Arrays;
+
+import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class SaveOptimizeForSpeedTest {
+
+    // longer than the 512 char chunk OptimizedForSpeedSaver emits comment/pi text in
+    private static final String LONG = repeat('a', 1500);
+
+    private static String repeat(char c, int n) {
+        char[] a = new char[n];
+        Arrays.fill(a, c);
+        return new String(a);
+    }
+
+    private static String saveForSpeed(XmlObject o) throws Exception {
+        XmlOptions opts = new XmlOptions();
+        opts.setSaveOptimizeForSpeed(true);
+        StringWriter sw = new StringWriter();
+        o.save(sw, opts);
+        return sw.toString();
+    }
+
+    @Test
+    void testLongCommentSavesForSpeed() throws Exception {
+        XmlObject o = XmlObject.Factory.parse("<root><!--" + LONG + "--></root>");
+        String out = saveForSpeed(o);
+        XmlObject.Factory.parse(out);
+        assertTrue(out.contains(LONG));
+    }
+
+    @Test
+    void testLongProcInstSavesForSpeed() throws Exception {
+        // pi text of 1024 chars or more spins forever before the fix
+        String out = assertTimeoutPreemptively(Duration.ofSeconds(30), () -> {
+            XmlObject o = XmlObject.Factory.parse("<root><?tgt " + LONG + "?></root>");
+            return saveForSpeed(o);
+        });
+        XmlObject.Factory.parse(out);
+        assertTrue(out.contains(LONG));
+    }
+}