diff --git a/extensions/freebase/build.xml b/extensions/freebase/build.xml
index 7b88a086f..f40f07905 100644
--- a/extensions/freebase/build.xml
+++ b/extensions/freebase/build.xml
@@ -57,7 +57,7 @@
             
     <target name="build_java">
         <mkdir dir="${classes.dir}" />
-        <javac encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
+        <javac  source="${java_version}" target="${java_version}" encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
             <src path="${src.dir}"/>
             <classpath refid="class.path" />
         </javac>
diff --git a/extensions/gdata/build.xml b/extensions/gdata/build.xml
index 51cb9b9ce..0a344cbf2 100644
--- a/extensions/gdata/build.xml
+++ b/extensions/gdata/build.xml
@@ -2,8 +2,8 @@
 
 <!--+
     |
-    |  OpenRefine GData Extension Build File    
-    |                
+    |  OpenRefine GData Extension Build File
+    |
     +-->
     
 <project name="grefine-gdata-extension" default="build" basedir=".">
@@ -50,7 +50,7 @@
             
     <target name="build_java">
         <mkdir dir="${classes.dir}" />
-        <javac encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
+        <javac  source="${java_version}" target="${java_version}" encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
             <src path="${src.dir}"/>
             <classpath refid="class.path" />
         </javac>
diff --git a/extensions/jython/build.xml b/extensions/jython/build.xml
index 12bdaa729..4b4f151b0 100644
--- a/extensions/jython/build.xml
+++ b/extensions/jython/build.xml
@@ -52,7 +52,7 @@
             
     <target name="build_java">
         <mkdir dir="${classes.dir}" />
-        <javac encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
+        <javac  source="${java_version}" target="${java_version}" encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
             <src path="${src.dir}"/>
             <classpath refid="class.path" />
         </javac>
diff --git a/extensions/pc-axis/build.xml b/extensions/pc-axis/build.xml
index 6fb950bff..3682348d7 100644
--- a/extensions/pc-axis/build.xml
+++ b/extensions/pc-axis/build.xml
@@ -53,7 +53,7 @@
 
     <target name="build_java">
         <mkdir dir="${classes.dir}" />
-        <javac encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
+        <javac  source="${java_version}" target="${java_version}" encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
             <src path="${src.dir}"/>
             <classpath refid="class.path" />
         </javac>
diff --git a/extensions/sample/build.xml b/extensions/sample/build.xml
index 029760619..42e918946 100644
--- a/extensions/sample/build.xml
+++ b/extensions/sample/build.xml
@@ -57,7 +57,7 @@
             
     <target name="build_java">
         <mkdir dir="${classes.dir}" />
-        <javac encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
+        <javac source="${java_version}" target="${java_version}" encoding="utf-8" destdir="${classes.dir}" debug="true" includeAntRuntime="no">
             <src path="${src.dir}"/>
             <classpath refid="class.path" />
         </javac>