diff --git a/HowToBuild b/HowToBuild
index 8d78b41f5..e612eef9a 100644
--- a/HowToBuild
+++ b/HowToBuild
@@ -7,7 +7,9 @@ Prerequisites:
 
 2. Android NDK >= r4b
 
-3. Apache Ant >= 1.7.1
+3. Apache Ant >= 1.7.0
+
+4. (Windows-only) Cygwin >= 1.7
 
 To build:
 
diff --git a/build.xml b/build.xml
index 7cbe072d9..113a6021a 100644
--- a/build.xml
+++ b/build.xml
@@ -19,21 +19,21 @@
 	<setup />
 
 	<target name="init" description="Initialization...">
-		<condition property="Ant17isOnline">
-			<and>
-				<antversion property="ant.version" atleast="1.7.0"/>
-			</and>
-		</condition>
 		<fail message="ANT with version at least 1.7 should be present !!! Update your local '${ant.version}' first.">
 			<condition>
 				<not>
-					<isset property="Ant17isOnline"/>
+					<antversion property="ant.version" atleast="1.7.0"/>
 				</not>
 			</condition>
 		</fail>
 	</target>
 
 	<target name="native" unless="native.lib.is.built">
+		<fail message="Native libraries are not up-to-date. Please run ndk-build manually.">
+			<condition>
+				<os family="windows" />
+			</condition>
+		</fail>
 		<echo message="Try to build 'libDeflatingDecompressor.so', 'libLineBreak.so'...."/>
 		<exec executable="${ndk.dir}/ndk-build" />
 	</target>