diff --git a/NEWS.md b/NEWS.md
index 69aa135..806cb8e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,17 @@
+Release 1.6.6: 11th January 2026
+--------------------------------
+
+This is a bug fix release.
+
+Bug fixes
+
+- Prevent use of unaligned 16-bit integers from memmove.
+  (PR #145 Robert Davies)
+
+- Add missing support for X_CAT in arithmetic codec.
+  (PR #146; Issue #144 Michael Macias)
+
+
 Release 1.6.5: 9th December 2025
 --------------------------------
 
diff --git a/configure.ac b/configure.ac
index 082783a..9cce9f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-AC_INIT(htscodecs, 1.6.5)
+AC_INIT(htscodecs, 1.6.6)
 
 # Some functions benefit from -O3 optimisation, so if the user didn't
 # explicitly set any compiler flags, we'll plump for O3.
@@ -61,7 +61,7 @@ AM_EXTRA_RECURSIVE_TARGETS([fuzz])
 #       libhtscodecs.so.1.1.0
 
 VERS_CURRENT=3
-VERS_REVISION=10
+VERS_REVISION=11
 VERS_AGE=1
 AC_SUBST(VERS_CURRENT)
 AC_SUBST(VERS_REVISION)
diff --git a/htscodecs/htscodecs.h b/htscodecs/htscodecs.h
index dfce5c1..d766dfa 100644
--- a/htscodecs/htscodecs.h
+++ b/htscodecs/htscodecs.h
@@ -43,7 +43,7 @@
  * Note currently this needs manually editing as it isn't automatically
  * updated by autoconf.
  */
-#define HTSCODECS_VERSION 100605
+#define HTSCODECS_VERSION 100606
 
 /*
  * A const string form of the HTSCODECS_VERSION define.