diff --git a/httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CacheControlHeaderParser.java b/httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CacheControlHeaderParser.java
index c1dad40b08..6aae254507 100644
--- a/httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CacheControlHeaderParser.java
+++ b/httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CacheControlHeaderParser.java
@@ -230,7 +230,11 @@ public final RequestCacheControl parseRequest(final Iterator<Header> headerItera
             if (name.equalsIgnoreCase(HeaderConstants.CACHE_CONTROL_MAX_AGE)) {
                 builder.setMaxAge(parseSeconds(name, value));
             } else if (name.equalsIgnoreCase(HeaderConstants.CACHE_CONTROL_MAX_STALE)) {
-                builder.setMaxStale(parseSeconds(name, value));
+                if (value == null) {
+                    builder.setMaxStale(Long.MAX_VALUE);
+                } else {
+                    builder.setMaxStale(parseSeconds(name, value));
+                }
             } else if (name.equalsIgnoreCase(HeaderConstants.CACHE_CONTROL_MIN_FRESH)) {
                 builder.setMinFresh(parseSeconds(name, value));
             } else if (name.equalsIgnoreCase(HeaderConstants.CACHE_CONTROL_NO_STORE)) {
diff --git a/httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/CacheControlParserTest.java b/httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/CacheControlParserTest.java
index d4ad639190..49f6c3609b 100644
--- a/httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/CacheControlParserTest.java
+++ b/httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/CacheControlParserTest.java
@@ -259,4 +259,23 @@ void testParseMultipleIsImmutable() {
         assertTrue(cacheControl.isImmutable());
     }
 
+    @Test
+    void testParseRequestMaxStaleWithoutValue() {
+        // RFC 9111: "max-stale" without a value means accept any staleness
+        final Header header = new BasicHeader("Cache-Control", "max-stale");
+        final RequestCacheControl cacheControl = parser.parseRequest(Collections.singletonList(header).iterator());
+
+        assertEquals(Long.MAX_VALUE, cacheControl.getMaxStale());
+    }
+
+    @Test
+    void testParseRequestMaxStaleEmptyValueIsInvalid() {
+        // "max-stale=" is not the same as bare "max-stale" (missing delta-seconds)
+        final Header header = new BasicHeader("Cache-Control", "max-stale=");
+        final RequestCacheControl cacheControl = parser.parseRequest(Collections.singletonList(header).iterator());
+
+        assertEquals(-1L, cacheControl.getMaxStale());
+    }
+
+
 }