diff --git a/lib/modules/SSL.pmod/State.pike b/lib/modules/SSL.pmod/State.pike
index 93f9ed28ec457db4640b9dd5af1858ccae102fad..6405950cc06d4d82e372e4eaf9001387fab3c4a9 100644
--- a/lib/modules/SSL.pmod/State.pike
+++ b/lib/modules/SSL.pmod/State.pike
@@ -27,7 +27,7 @@ Cipher.MACAlgorithm mac;
 //! Encryption or decryption object.
 Cipher.CipherAlgorithm crypt;
 
-function(string:string) compress;
+function(string(8bit),int(1bit)|void:string(8bit)) compress;
 
 //! 64-bit sequence number.
 int seq_num = 0;    /* Bignum, values 0, .. 2^64-1 are valid */