diff --git a/contrib/pgcrypto/px.c b/contrib/pgcrypto/px.c
index ed7e330edc2..0fa6dbc2c77 100644
--- a/contrib/pgcrypto/px.c
+++ b/contrib/pgcrypto/px.c
@@ -26,7 +26,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $Id: px.c,v 1.7 2002/03/06 06:09:10 momjian Exp $
+ * $Id: px.c,v 1.7.6.1 2007/08/23 16:16:20 tgl Exp $
  */
 
 #include <postgres.h>
@@ -185,6 +185,18 @@ combo_decrypt(PX_Combo * cx, const uint8 *data, unsigned dlen,
 
 	PX_Cipher  *c = cx->cipher;
 
+	/* decide whether zero-length input is allowed */
+	if (dlen == 0)
+	{
+		/* with padding, empty ciphertext is not allowed */
+		if (cx->padding)
+			return -1;
+		
+		/* without padding, report empty result */
+		*rlen = 0;
+		return 0;
+	}
+
 	bs = px_cipher_block_size(c);
 	if (bs > 1 && (dlen % bs) != 0)
 		goto block_error;