diff --git a/CHANGELOG b/CHANGELOG
index d54f6ff2c..8a6b8e525 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o Fixed CRC32c calculation (as used in SCTP scans) on 64-bit
+  platforms. [Pontus Andersson]
+
 o [NSE] Added multicast group name output to
   broadcast-igmp-discovery.nse. [Vasily Kulikov]
 
diff --git a/nbase/nbase_misc.c b/nbase/nbase_misc.c
index fc4179d3a..391ab19f6 100644
--- a/nbase/nbase_misc.c
+++ b/nbase/nbase_misc.c
@@ -560,14 +560,17 @@ unsigned long nbase_crc32(unsigned char *buf, int len)
 
 /*
  * CRC-32C (Castagnoli) Cyclic Redundancy Check.
- * Taken straight from RFC 4960 (SCTP).
+ * Taken straight from Appendix C of RFC 4960 (SCTP), with the difference that
+ * the remainder register (crc32) is initialized to 0xffffffffL rather than ~0L,
+ * for correct operation on platforms where unisigned long is longer than 32
+ * bits.
  */
 
 /* Return the CRC-32C of the bytes buf[0..len-1] */
 unsigned long nbase_crc32c(unsigned char *buf, int len)
 {
   int i;
-  unsigned long crc32 = ~0L;
+  unsigned long crc32 = 0xffffffffL;
   unsigned long result;
   unsigned char byte0, byte1, byte2, byte3;