diff --git a/src/etc/testcases/taskdefs/property.xml b/src/etc/testcases/taskdefs/property.xml
index 75fbe6940..00bfbcdda 100644
--- a/src/etc/testcases/taskdefs/property.xml
+++ b/src/etc/testcases/taskdefs/property.xml
@@ -36,4 +36,9 @@
     <property name="someprop" value="value" prefix="prefix"/>
   </target>
 
+  <!-- caused an endless loop, PR 21825 -->
+  <target name="testCircularReference">
+    <property file="property4.properties"/>
+  </target>
+
 </project>
diff --git a/src/etc/testcases/taskdefs/property4.properties b/src/etc/testcases/taskdefs/property4.properties
new file mode 100644
index 000000000..d2af886e5
--- /dev/null
+++ b/src/etc/testcases/taskdefs/property4.properties
@@ -0,0 +1,2 @@
+a=${a}
+b=${a}/b
diff --git a/src/main/org/apache/tools/ant/taskdefs/Property.java b/src/main/org/apache/tools/ant/taskdefs/Property.java
index 2fe2c36aa..ae998571c 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Property.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Property.java
@@ -573,6 +573,8 @@ public class Property extends Task {
             String value = props.getProperty(name);
 
             boolean resolved = false;
+            Vector expandedReferences = new Vector();
+            expandedReferences.addElement(name);
             while (!resolved) {
                 Vector fragments = new Vector();
                 Vector propertyRefs = new Vector();
@@ -588,11 +590,12 @@ public class Property extends Task {
                         String fragment = (String) i.nextElement();
                         if (fragment == null) {
                             String propertyName = (String) j.nextElement();
-                            if (propertyName.equals(name)) {
+                            if (expandedReferences.contains(propertyName)) {
                                 throw new BuildException("Property " + name
                                                          + " was circularly "
                                                          + "defined.");
                             }
+                            expandedReferences.addElement(propertyName);
                             fragment = getProject().getProperty(propertyName);
                             if (fragment == null) {
                                 if (props.containsKey(propertyName)) {
diff --git a/src/testcases/org/apache/tools/ant/taskdefs/PropertyTest.java b/src/testcases/org/apache/tools/ant/taskdefs/PropertyTest.java
index 0fe9ea09c..2ba10b657 100644
--- a/src/testcases/org/apache/tools/ant/taskdefs/PropertyTest.java
+++ b/src/testcases/org/apache/tools/ant/taskdefs/PropertyTest.java
@@ -116,4 +116,16 @@ public class PropertyTest extends BuildFileTest {
         fail("Did not throw exception on invalid use of prefix");
     }
 
+    public void testCircularReference() {
+        try {
+            executeTarget("testCircularReference");
+        } catch (BuildException e) {
+            assertEquals("Circular definition not detected - ", true,
+                         e.getMessage().indexOf("was circularly defined") 
+                         != -1);
+            return;
+        }
+        fail("Did not throw exception on circular exception");
+    }
+
 }