diff --git a/src/main/java/com/android/tools/r8/ClassFileConsumer.java b/src/main/java/com/android/tools/r8/ClassFileConsumer.java
index 3521429..364a794 100644
--- a/src/main/java/com/android/tools/r8/ClassFileConsumer.java
+++ b/src/main/java/com/android/tools/r8/ClassFileConsumer.java
@@ -161,7 +161,7 @@
             String className = resource.getClassDescriptors().iterator().next();
             String entryName = getClassFileName(className);
             byte[] bytes = ByteStreams.toByteArray(closer.register(resource.getByteStream()));
-            ZipUtils.writeToZipStream(out, entryName, bytes, ZipEntry.STORED);
+            ZipUtils.writeToZipStream(out, entryName, bytes, ZipEntry.DEFLATED);
           }
         }
       }
diff --git a/src/main/java/com/android/tools/r8/utils/ArchiveBuilder.java b/src/main/java/com/android/tools/r8/utils/ArchiveBuilder.java
index 69d65ea..2276790 100644
--- a/src/main/java/com/android/tools/r8/utils/ArchiveBuilder.java
+++ b/src/main/java/com/android/tools/r8/utils/ArchiveBuilder.java
@@ -150,7 +150,7 @@
 
   private void writeFileNow(String name, ByteDataView content, DiagnosticsHandler handler) {
     try {
-      ZipUtils.writeToZipStream(getStream(handler), name, content, ZipEntry.STORED);
+      ZipUtils.writeToZipStream(getStream(handler), name, content, ZipEntry.DEFLATED);
     } catch (IOException e) {
       handleIOException(e, handler);
     }
diff --git a/tools/run_bootstrap_benchmark.py b/tools/run_bootstrap_benchmark.py
index ad26959..9f2f7e4 100755
--- a/tools/run_bootstrap_benchmark.py
+++ b/tools/run_bootstrap_benchmark.py
@@ -60,11 +60,11 @@
       sys.exit(return_code)
 
     dex(r8_output, d8_r8_output)
-    print "BootstrapR8(CodeSize):", os.path.getsize(r8_output)
-    print "BootstrapR8Dex(CodeSize):", os.path.getsize(d8_r8_output)
+    print "BootstrapR8(CodeSize):", utils.uncompressed_size(r8_output)
+    print "BootstrapR8Dex(CodeSize):", utils.uncompressed_size(d8_r8_output)
 
     dex(PINNED_PGR8_JAR, d8_pg_output)
-    print "BootstrapR8PG(CodeSize):", os.path.getsize(PINNED_PGR8_JAR)
-    print "BootstrapR8PGDex(CodeSize):", os.path.getsize(d8_pg_output)
+    print "BootstrapR8PG(CodeSize):", utils.uncompressed_size(PINNED_PGR8_JAR)
+    print "BootstrapR8PGDex(CodeSize):", utils.uncompressed_size(d8_pg_output)
 
   sys.exit(0)
diff --git a/tools/utils.py b/tools/utils.py
index bd54dbc..682213a 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -12,6 +12,7 @@
 import sys
 import tarfile
 import tempfile
+import zipfile
 
 ANDROID_JAR = 'third_party/android_jar/lib-v{api}/android.jar'
 TOOLS_DIR = os.path.abspath(os.path.normpath(os.path.join(__file__, '..')))
@@ -308,3 +309,9 @@
 
 def is_bot():
   return 'BUILDBOT_BUILDERNAME' in os.environ
+
+
+def uncompressed_size(path):
+  return sum(z.file_size for z in zipfile.ZipFile(path).infolist())
+
+