diff --git a/httpcore5/src/main/java/org/apache/hc/core5/net/URIBuilder.java b/httpcore5/src/main/java/org/apache/hc/core5/net/URIBuilder.java
index febe0f5cb..eb84ab41c 100644
--- a/httpcore5/src/main/java/org/apache/hc/core5/net/URIBuilder.java
+++ b/httpcore5/src/main/java/org/apache/hc/core5/net/URIBuilder.java
@@ -207,7 +207,7 @@ public URIBuilder setCharset(final Charset charset) {
      * Sets the encoding policy for this {@link URIBuilder}.
      * The encoding policy determines how URI components (e.g., query, fragment) are
      * percent-encoded when building the URI string. If not set, the default policy
-     * is {@link EncodingPolicy#RFC_3986}.
+     * is {@link EncodingPolicy#ALL_RESERVED}.
      *
      * @param encodingPolicy the encoding policy to apply, or {@code null} to reset
      *                       to the default ({@link EncodingPolicy#ALL_RESERVED})
@@ -215,7 +215,7 @@ public URIBuilder setCharset(final Charset charset) {
      * @since 5.4
      */
     public URIBuilder setEncodingPolicy(final EncodingPolicy encodingPolicy) {
-        this.encodingPolicy = encodingPolicy;
+        this.encodingPolicy = encodingPolicy != null ? encodingPolicy : EncodingPolicy.ALL_RESERVED;
         return this;
     }
 
diff --git a/httpcore5/src/test/java/org/apache/hc/core5/net/TestURIBuilder.java b/httpcore5/src/test/java/org/apache/hc/core5/net/TestURIBuilder.java
index 3483309a3..42d0f00e2 100644
--- a/httpcore5/src/test/java/org/apache/hc/core5/net/TestURIBuilder.java
+++ b/httpcore5/src/test/java/org/apache/hc/core5/net/TestURIBuilder.java
@@ -976,6 +976,39 @@ void testSetPlusAsBlank() throws Exception {
         Assertions.assertEquals("hello world", params.get(0).getValue());
     }
 
+    @Test
+    void testDefaultEncodingPolicy() throws Exception {
+        final URIBuilder builder = new URIBuilder()
+                .setScheme("http")
+                .setHost("example.com")
+                .setPath("/a:b")
+                .addParameter("key", "a/b")
+                .setFragment("a/b");
+        final URI expected = new URI("http://example.com/a%3Ab?key=a%2Fb#a%2Fb");
+
+        Assertions.assertEquals(expected, builder.build());
+        builder.setEncodingPolicy(URIBuilder.EncodingPolicy.ALL_RESERVED);
+        Assertions.assertEquals(expected, builder.build());
+        builder.setEncodingPolicy(null);
+        Assertions.assertEquals(expected, builder.build());
+    }
+
+    @Test
+    void testResetEncodingPolicy() throws Exception {
+        final URIBuilder builder = new URIBuilder()
+                .setScheme("http")
+                .setUserInfo("user!")
+                .setHost("example.com")
+                .setPath("/a:b")
+                .setCustomQuery("a/b")
+                .setFragment("a/b")
+                .setEncodingPolicy(URIBuilder.EncodingPolicy.RFC_3986);
+
+        Assertions.assertEquals(new URI("http://user!@example.com/a:b?a/b#a/b"), builder.build());
+        Assertions.assertSame(builder, builder.setEncodingPolicy(null));
+        Assertions.assertEquals(new URI("http://user%21@example.com/a%3Ab?a%2Fb#a%2Fb"), builder.build());
+    }
+
     @Test
     void testCustomQueryEncoding() throws Exception {
         final String query = "query param:!@/?\"";