diff --git a/csv/src/main/java/com/fasterxml/jackson/dataformat/csv/CsvSchema.java b/csv/src/main/java/com/fasterxml/jackson/dataformat/csv/CsvSchema.java
index eecc326e..0df3b8de 100644
--- a/csv/src/main/java/com/fasterxml/jackson/dataformat/csv/CsvSchema.java
+++ b/csv/src/main/java/com/fasterxml/jackson/dataformat/csv/CsvSchema.java
@@ -9,6 +9,9 @@
 /**
  * Simple {@link FormatSchema} sub-type that defines properties of
  * a CSV document to read or write.
+ * Instances are thread-safe and immutable (explicitly immutable since 2.19,
+ * but thread-safe since 2.0).
+ * <p>
  * Properties supported currently are:
  *<ul>
  * <li>{@code columns} (List of ColumnDef) [default: empty List]: Ordered list of columns (which may be empty, see below).
@@ -885,9 +888,9 @@ protected void _checkIndex(int index) {
     /**
      * Bitflag for general-purpose on/off features.
      * 
-     * @since 2.5
+     * @since 2.5 (final since 2.19)
      */
-    protected int _features = DEFAULT_ENCODING_FEATURES;
+    protected final int _features;
 
     protected final char _columnSeparator;
 
diff --git a/release-notes/CREDITS-2.x b/release-notes/CREDITS-2.x
index 88dc90b0..62d72a0b 100644
--- a/release-notes/CREDITS-2.x
+++ b/release-notes/CREDITS-2.x
@@ -289,3 +289,9 @@ Robert DiFalco (@rdifalco)
 
 * Reported #31: Header names seem to be trimmed
  (2.19.0)
+
+Gili Tzabari (@cowwoc)
+
+* Requested #554: (csv) Enforce, document thread-safety of `CsvSchema`
+ (2.19.0)
+
diff --git a/release-notes/VERSION-2.x b/release-notes/VERSION-2.x
index 2f45cb6f..eb3f448d 100644
--- a/release-notes/VERSION-2.x
+++ b/release-notes/VERSION-2.x
@@ -25,6 +25,8 @@ Active Maintainers:
  (contributed by Joo-Hyuk K)
 #537: (yaml) Snakeyaml 2.4
  (contributed by @pjfanning)
+#554: (csv) Enforce, document thread-safety of `CsvSchema`
+ (requested by Gili T)
 
 2.18.3 (28-Feb-2025)
 2.18.2 (27-Nov-2024)