diff --git a/src/main/org/apache/tools/ant/IntrospectionHelper.java b/src/main/org/apache/tools/ant/IntrospectionHelper.java
index d4bf771..a3218d8 100644
--- a/src/main/org/apache/tools/ant/IntrospectionHelper.java
+++ b/src/main/org/apache/tools/ant/IntrospectionHelper.java
@@ -320,7 +320,7 @@ public final class IntrospectionHelper {
      *
      * @return a helper for the specified class
      */
-    public static synchronized IntrospectionHelper getHelper(final Class<?> c) {
+    public static IntrospectionHelper getHelper(final Class<?> c) {
         return getHelper(null, c);
     }
 
@@ -337,7 +337,7 @@ public final class IntrospectionHelper {
      *
      * @return a helper for the specified class
      */
-    public static synchronized IntrospectionHelper getHelper(final Project p, final Class<?> c) {
+    public static IntrospectionHelper getHelper(final Project p, final Class<?> c) {
         IntrospectionHelper ih = HELPERS.get(c.getName());
         // If a helper cannot be found, or if the helper is for another
         // classloader, create a new IH
@@ -346,7 +346,13 @@ public final class IntrospectionHelper {
             if (p != null) {
                 // #30162: do *not* cache this if there is no project, as we
                 // cannot guarantee that the cache will be cleared.
-                HELPERS.put(c.getName(), ih);
+                synchronized (HELPERS) {
+                    IntrospectionHelper oh = HELPERS.get(c.getName());
+                    if (oh != null)
+                        ih = oh;
+                    else
+                        HELPERS.put(c.getName(), ih);
+                }
             }
         }
         return ih;