diff --git a/NEWS b/NEWS
index da5c09a2..7bcbd142 100644
--- a/NEWS
+++ b/NEWS
@@ -92,6 +92,7 @@ Changes since version 6.4:
     - Terminal mode: memory fill with strings may cause Avrdude to crash. #922
     - Some parts have wrong or missing ISP commands #915
     - Incorrect -b conversion for linuxspi programmer #927
+    - ATtiny43U calibration memory size #921
 
   * Pull requests:
 
diff --git a/src/avrdude.conf.in b/src/avrdude.conf.in
index d33a26a3..362b6167 100644
--- a/src/avrdude.conf.in
+++ b/src/avrdude.conf.in
@@ -12888,7 +12888,7 @@ part
     ;
 
     memory "calibration"
-        size            = 2;
+        size            = 1;
         read            = "0  0  1  1   1  0  0  0    0 0 0 x  x x x x",
                           "0  0  0  0   0  0  0  a0   o o o o  o o o o";
     ;