diff --git a/platform/util/src/com/intellij/util/io/zip/JBZipEntry.java b/platform/util/src/com/intellij/util/io/zip/JBZipEntry.java
index 1f740ec0a3e3..a3b025ddd8c8 100644
--- a/platform/util/src/com/intellij/util/io/zip/JBZipEntry.java
+++ b/platform/util/src/com/intellij/util/io/zip/JBZipEntry.java
@@ -343,7 +343,7 @@ public class JBZipEntry {
     long start = calcDataOffset();
     long size = getCompressedSize();
     myFile.ensureFlushed(start + size);
-    if (myFile.myArchive.size() < start + size) {
+    if (myFile.getSize() < start + size) {
       throw new EOFException();
     }
     BoundedInputStream bis = new BoundedInputStream(start, size);
diff --git a/platform/util/src/com/intellij/util/io/zip/JBZipFile.java b/platform/util/src/com/intellij/util/io/zip/JBZipFile.java
index c08816390a5c..25ce13f688d1 100644
--- a/platform/util/src/com/intellij/util/io/zip/JBZipFile.java
+++ b/platform/util/src/com/intellij/util/io/zip/JBZipFile.java
@@ -92,7 +92,8 @@ public class JBZipFile implements Closeable {
 
   private JBZipOutputStream myOutputStream;
   private long currentCfdOffset;
-  private final boolean myIsReadonly;
+  final boolean myIsReadonly;
+  private final long mySize;
 
 
   /**
@@ -197,10 +198,17 @@ public class JBZipFile implements Closeable {
   public JBZipFile(@NotNull SeekableByteChannel channel, @NotNull Charset encoding, boolean readonly, @NotNull ThreeState isZip64) throws IOException {
     myEncoding = encoding;
     myIsReadonly = readonly;
+    long channelSize = channel.size();
+    if (readonly) {
+      mySize = channelSize;
+    }
+    else {
+      mySize = -1;
+    }
     myArchive = channel;
 
     try {
-      if (myArchive.size() > 0) {
+      if (channelSize > 0) {
         populateFromCentralDirectory(isZip64);
       }
       else {
@@ -326,7 +334,7 @@ public class JBZipFile implements Closeable {
       instead gaining a performance boost.
      */
     ByteBuffer centralDirectoryCached = ByteBuffer.allocate(
-      Math.min((int)(myArchive.size() - myArchive.position()),
+      Math.min((int)(getSize() - myArchive.position()),
                // Sometimes the size of the central directory may be significant -- up to 3 megabytes.
                64 * 1024) // seems enough
     );
@@ -573,7 +581,7 @@ public class JBZipFile implements Closeable {
    */
   private void positionAtCentralDirectory(@NotNull ThreeState isZip64) throws IOException {
     boolean found = false;
-    long off = myArchive.size() - MIN_EOCD_SIZE;
+    long off = getSize() - MIN_EOCD_SIZE;
     if (off >= 0) {
       myArchive.position(off);
       byte[] sig = JBZipOutputStream.EOCD_SIG;
@@ -720,4 +728,13 @@ public class JBZipFile implements Closeable {
   void ensureFlushed(long end) throws IOException {
     if (myOutputStream != null) myOutputStream.ensureFlushed(end);
   }
+
+  long getSize() throws IOException {
+    if (mySize == -1) {
+      return myArchive.size();
+    }
+    else {
+      return mySize;
+    }
+  }
 }