diff --git a/WHATSNEW b/WHATSNEW
index 9d738dfa7..a58f3c462 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -100,6 +100,12 @@ Fixed bugs:
    tasks were trying to create the same directory.
    Bugzilla Report 49572.
 
+ * the toString() method of the Resources class - and thus any
+   ${toString:} expansion of a reference to a <resources> element -
+   didn't iterate over its nested elements if it hadn't done so prior
+   to the toString invocation already.
+   Bugzilla Report 49588.
+
 Other changes:
 --------------
 
diff --git a/src/main/org/apache/tools/ant/types/resources/Resources.java b/src/main/org/apache/tools/ant/types/resources/Resources.java
index 99143739b..1599bb80a 100644
--- a/src/main/org/apache/tools/ant/types/resources/Resources.java
+++ b/src/main/org/apache/tools/ant/types/resources/Resources.java
@@ -208,6 +208,7 @@ public class Resources extends DataType implements ResourceCollection {
         if (isReference()) {
             return getCheckedRef().toString();
         }
+        validate();
         if (coll == null || coll.isEmpty()) {
             return "";
         }
diff --git a/src/tests/antunit/types/resources/resources-test.xml b/src/tests/antunit/types/resources/resources-test.xml
new file mode 100644
index 000000000..19985c721
--- /dev/null
+++ b/src/tests/antunit/types/resources/resources-test.xml
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+-->
+<project default="antunit" xmlns:au="antlib:org.apache.ant.antunit">
+
+  <import file="../../antunit-base.xml"/>
+
+  <target name="testToString"
+          description="https://issues.apache.org/bugzilla/show_bug.cgi?id=49588">
+    <resources id="A">
+      <string value="b"/>
+    </resources>
+    <union id="union"><resources refid="A"/></union>
+    <au:assertEquals expected="b" actual="${toString:A}"/>
+    <au:assertEquals expected="b" actual="${toString:union}"/>
+    <au:assertEquals expected="b" actual="${toString:A}"/>
+  </target>
+</project>