diff --git a/build.xml b/build.xml
index 52dfe71..0d41bdf 100644
--- a/build.xml
+++ b/build.xml
@@ -721,8 +721,12 @@ The text for an official release would continue like ...
             <arg path="${out}"/>
             <arg value="-lib"/>
             <arg path="${out}"/>
-            <arg file="${basedir}/grammar/Python.g"/>
-            <arg file="${basedir}/grammar/PythonPartial.g"/>
+            <!-- Reproducible builds
+                 Replace 'arg file=...' with 'arg value=...' to prevent using
+                 the absolute filename, because these filenames are inserted
+                 into the antlr generated getGrammar* methods -->
+            <arg value="grammar/Python.g"/>
+            <arg value="grammar/PythonPartial.g"/>
             <classpath refid="main.classpath"/>
         </java>
 
@@ -1151,7 +1155,10 @@ The text for an official release would continue like ...
     </target>
 
     <target name="copy-lib" depends="common-dirs, copy-cpythonlib">
-        <copy todir="${dist.dir}/Lib">
+        <!-- Reproducible builds
+             Use attribute preservelastmodified="true" because these files'
+             mtime are stored into the generated $py.class files -->
+        <copy todir="${dist.dir}/Lib" preservelastmodified="true">
             <fileset dir="${basedir}/Lib">
                 <exclude name="**/*.class"/>
             </fileset>
@@ -1175,7 +1182,10 @@ The text for an official release would continue like ...
         <copy file="${basedir}/lib-python/LICENSE.txt"
               tofile="${dist.dir}/LICENSE_CPython.txt"
               preservelastmodified="true" />
-        <copy todir="${dist.dir}/Lib">
+        <!-- Reproducible builds
+             Use attribute preservelastmodified="true" because these files'
+             mtime are stored into the generated $py.class files -->
+        <copy todir="${dist.dir}/Lib" preservelastmodified="true">
             <fileset dir="${python.lib}" excludes="**/*.pyc, **/*.pyo" includesfile="${basedir}/CPythonLib.includes">
                 <!-- The include file gets all of lib-python/2.7's test directory, but we only want the ones from Jython's Lib.   -->
                 <present present="srconly" targetdir="${basedir}/Lib"/>