diff --git a/java-spiffe-core/src/main/java/io/spiffe/workloadapi/CachedJwtSource.java b/java-spiffe-core/src/main/java/io/spiffe/workloadapi/CachedJwtSource.java
index 32b04db4..2318e63d 100644
--- a/java-spiffe-core/src/main/java/io/spiffe/workloadapi/CachedJwtSource.java
+++ b/java-spiffe-core/src/main/java/io/spiffe/workloadapi/CachedJwtSource.java
@@ -44,7 +44,7 @@ public class CachedJwtSource implements JwtSource {
     private final
     Map<ImmutablePair<SpiffeId, Set<String>>, List<JwtSvid>> jwtSvids = new ConcurrentHashMap<>();
 
-    private JwtBundleSet bundles;
+    private volatile JwtBundleSet bundles;
 
     private final WorkloadApiClient workloadApiClient;
     private volatile boolean closed;
diff --git a/java-spiffe-core/src/main/java/io/spiffe/workloadapi/DefaultJwtSource.java b/java-spiffe-core/src/main/java/io/spiffe/workloadapi/DefaultJwtSource.java
index 96e58057..ed5699fb 100644
--- a/java-spiffe-core/src/main/java/io/spiffe/workloadapi/DefaultJwtSource.java
+++ b/java-spiffe-core/src/main/java/io/spiffe/workloadapi/DefaultJwtSource.java
@@ -33,7 +33,7 @@ public class DefaultJwtSource implements JwtSource {
     static final Duration DEFAULT_TIMEOUT =
             Duration.parse(System.getProperty(TIMEOUT_SYSTEM_PROPERTY, "PT0S"));
 
-    private JwtBundleSet bundles;
+    private volatile JwtBundleSet bundles;
 
     private final WorkloadApiClient workloadApiClient;
     private volatile boolean closed;