diff --git a/README.md b/README.md
index 1a175dd..4984440 100644
--- a/README.md
+++ b/README.md
@@ -8,4 +8,13 @@ go to them. This is merely a few bugfixes and improvements.
 Original code and information can be found here: 
 https://mdfs.net/Software/PDP11/BBCBasic/
 
+Changes from the original
+-------------------------
+* Swapped words of the `MT_ReadTime` function
 
+Running under RT11 5.4 it was found that the `TIME` variable
+was ticking around 60 million times too fast. Experiments
+showed that it was likely the words of the result being swapped.
+Patching BASIC to return the words in the opposite order (#1691d98)
+fixed the problem and TIME now ticks at the expected centisecond
+rate