diff --git a/src/main/org/apache/tools/ant/PropertyHelper.java b/src/main/org/apache/tools/ant/PropertyHelper.java
index c436657e9..67a27ff92 100644
--- a/src/main/org/apache/tools/ant/PropertyHelper.java
+++ b/src/main/org/apache/tools/ant/PropertyHelper.java
@@ -1117,4 +1117,43 @@ public class PropertyHelper implements GetProperty {
         return result;
     }
 
+    /**
+     * If the given object can be interpreted as a true/false value,
+     * turn it into a matching Boolean - otherwise return null.
+     * @since Ant 1.8.0
+     */
+    public static Boolean toBoolean(Object value) {
+        if (value instanceof Boolean) {
+            return (Boolean) value;
+        }
+        if (value instanceof String) {
+            String s = (String) value;
+            if (Project.toBoolean(s)) {
+                return Boolean.TRUE;
+            }
+            if ("off".equalsIgnoreCase(s)
+                || "false".equalsIgnoreCase(s)
+                || "no".equalsIgnoreCase(s)) {
+                return Boolean.FALSE;
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Returns true if the value is not-null, can be interpreted as a
+     * true value or cannot be interpreted as a false value and a
+     * property of the value's name exists.
+     * @since Ant 1.8.0
+     */
+    public boolean testIfCondition(Object value) {
+        if (value == null) {
+            return false;
+        }
+        Boolean b = toBoolean(value);
+        if (b != null) {
+            return b.booleanValue();
+        }
+        return getProperty(String.valueOf(value)) != null;
+    }
 }
diff --git a/src/main/org/apache/tools/ant/Target.java b/src/main/org/apache/tools/ant/Target.java
index f92369e35..66bb5a97a 100644
--- a/src/main/org/apache/tools/ant/Target.java
+++ b/src/main/org/apache/tools/ant/Target.java
@@ -462,10 +462,7 @@ public class Target implements TaskContainer {
         }
         PropertyHelper propertyHelper = PropertyHelper.getPropertyHelper(getProject());
         Object o = propertyHelper.parseProperties(ifCondition);
-        if (o instanceof Boolean) {
-            return ((Boolean) o).booleanValue();
-        }
-        return propertyHelper.getProperty(String.valueOf(o)) != null;
+        return propertyHelper.testIfCondition(o);
     }
 
     /**
@@ -483,9 +480,6 @@ public class Target implements TaskContainer {
         }
         PropertyHelper propertyHelper = PropertyHelper.getPropertyHelper(getProject());
         Object o = propertyHelper.parseProperties(unlessCondition);
-        if (o instanceof Boolean) {
-            return !((Boolean) o).booleanValue();
-        }
-        return propertyHelper.getProperty(String.valueOf(o)) == null;
+        return !propertyHelper.testIfCondition(o);
     }
 }
diff --git a/src/tests/antunit/core/target-test-helper.xml b/src/tests/antunit/core/target-test-helper.xml
index 924577b66..6ca2452f1 100644
--- a/src/tests/antunit/core/target-test-helper.xml
+++ b/src/tests/antunit/core/target-test-helper.xml
@@ -33,7 +33,25 @@
     <echo>unless-false called</echo>
   </target>
 
+  <target name="if-string-true" if="${true}">
+    <echo>if-string-true called</echo>
+  </target>
+
+  <target name="unless-string-true" unless="${true}">
+    <echo>unless-string-true called</echo>
+  </target>
+
+  <target name="if-string-false" if="${false}">
+    <echo>if-string-false called</echo>
+  </target>
+
+  <target name="unless-string-false" unless="${false}">
+    <echo>unless-string-false called</echo>
+  </target>
+
   <target name="all"
-          depends="if-true,unless-true,if-false,unless-false"/>
+          depends="if-true,unless-true,if-false,unless-false,
+                   if-string-true,unless-string-true,
+                   if-string-false,unless-string-false"/>
 
 </project>
diff --git a/src/tests/antunit/core/target-test.xml b/src/tests/antunit/core/target-test.xml
index 507a513b6..3e656be75 100644
--- a/src/tests/antunit/core/target-test.xml
+++ b/src/tests/antunit/core/target-test.xml
@@ -46,6 +46,10 @@ public class CreateBoolean extends ProjectComponent {
     <au:assertLogContains text="unless-false called"/>
     <au:assertLogDoesntContain text="if-true called"/>
     <au:assertLogDoesntContain text="if-false called"/>
+    <au:assertLogContains text="unless-string-true called"/>
+    <au:assertLogContains text="unless-string-false called"/>
+    <au:assertLogDoesntContain text="if-string-true called"/>
+    <au:assertLogDoesntContain text="if-string-false called"/>
   </target>
 
   <target name="testReferencesSet" depends="setUp">
@@ -55,5 +59,24 @@ public class CreateBoolean extends ProjectComponent {
     <au:assertLogContains text="unless-false called"/>
     <au:assertLogContains text="if-true called"/>
     <au:assertLogDoesntContain text="if-false called"/>
+    <au:assertLogContains text="unless-string-true called"/>
+    <au:assertLogContains text="unless-string-false called"/>
+    <au:assertLogDoesntContain text="if-string-true called"/>
+    <au:assertLogDoesntContain text="if-string-false called"/>
+  </target>
+
+  <target name="testProperttiesSet">
+    <ant antfile="target-test-helper.xml" target="all">
+      <property name="true" value="true"/>
+      <property name="false" value="false"/>
+    </ant>
+    <au:assertLogDoesntContain text="unless-string-true called"/>
+    <au:assertLogContains text="unless-string-false called"/>
+    <au:assertLogContains text="if-string-true called"/>
+    <au:assertLogDoesntContain text="if-string-false called"/>
+    <au:assertLogContains text="unless-true called"/>
+    <au:assertLogContains text="unless-false called"/>
+    <au:assertLogDoesntContain text="if-true called"/>
+    <au:assertLogDoesntContain text="if-false called"/>
   </target>
 </project>