--- a/dwt/internal/image/PngChunk.d	Wed Feb 06 11:08:01 2008 +0100
+++ b/dwt/internal/image/PngChunk.d	Wed Feb 06 12:09:44 2008 +0100
@@ -52,19 +52,28 @@
     static const byte[] TYPE_IEND = cast(byte[])"IEND";//{(byte) 'I', (byte) 'E', (byte) 'N', (byte) 'D'};
     static const byte[] TYPE_tRNS = cast(byte[])"tRNS";//{(byte) 't', (byte) 'R', (byte) 'N', (byte) 'S'};
 
-    static const int[] CRC_TABLE;
-    //public static void static_this() {
-    static this() {
-        CRC_TABLE = new int[256];
-        for (int i = 0; i < 256; i++) {
-            CRC_TABLE[i] = i;
-            for (int j = 0; j < 8; j++) {
-                if ((CRC_TABLE[i] & 0x1) is 0) {
-                    CRC_TABLE[i] = (CRC_TABLE[i] >> 1) & 0x7FFFFFFF;
-                } else {
-                    CRC_TABLE[i] = 0xEDB88320 ^ ((CRC_TABLE[i] >> 1) & 0x7FFFFFFF);
+    private static /+const+/ int[] CRC_TABLE;
+    private static bool static_this_completed = false;
+    private static void static_this() {
+        if( static_this_completed ){
+            return;
+        }
+        synchronized {
+            if( static_this_completed ){
+                return;
+            }
+            CRC_TABLE = new int[256];
+            for (int i = 0; i < 256; i++) {
+                CRC_TABLE[i] = i;
+                for (int j = 0; j < 8; j++) {
+                    if ((CRC_TABLE[i] & 0x1) is 0) {
+                        CRC_TABLE[i] = (CRC_TABLE[i] >> 1) & 0x7FFFFFFF;
+                    } else {
+                        CRC_TABLE[i] = 0xEDB88320 ^ ((CRC_TABLE[i] >> 1) & 0x7FFFFFFF);
+                    }
                 }
             }
+            static_this_completed = true;
         }
     }
 
@@ -75,6 +84,7 @@
  * given.
  */
 this(byte[] reference) {
+    static_this();
     setReference(reference);
     if (reference.length < LENGTH_OFFSET + LENGTH_FIELD_LENGTH) DWT.error(DWT.ERROR_INVALID_IMAGE);
     length = getInt32(LENGTH_OFFSET);