diff --git a/NEWS.md b/NEWS.md
index bd3017f51..6995aea0a 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -18,6 +18,8 @@
 
 - Part 1: Tidied up code in internal function detect_nonwear_clipping.R to ease future reviews. #1212
 
+- Part 4: Undo changes to 3 line in g.part4 function from commit 3b9e2b7 (in between 3.1-1 and 3.1-2 release in June 2024) which broke functionality for handling sleep that starts before the double DST hour in the autumn and ends inside it. #1221
+
 # CHANGES IN GGIR VERSION 3.1-4
 
 - Part 3: Update threshold used for HorAngle to 60 degree, and auto-setting HASPT.ignore.invalid to NA when NotWorn guider is used. #1186
diff --git a/R/g.part4.R b/R/g.part4.R
index e54482bb9..24fcbbfe8 100644
--- a/R/g.part4.R
+++ b/R/g.part4.R
@@ -814,9 +814,10 @@ g.part4 = function(datadir = c(), metadatadir = c(), f0 = f0, f1 = f1,
                   # in the autumn and ends inside the dst hour
                   negval = which(nocs < 0)
                   if (length(negval) > 0) {
-                    kk0 = as.numeric(spocum.t$start[negval])  # episode onsets
-                    kk1 = as.numeric(spocum.t$end[negval]) + 1 # episode endings
-                    nocs[negval] = kk1 - kk0
+                    kk0 = as.numeric(spocum.t$start[which(spocum.t$overlapGuider == 1)])  # episode onsets
+                    kk1 = as.numeric(spocum.t$end[which(spocum.t$overlapGuider == 1)])  # episode endings
+                    kk1[negval] = kk1[negval] + 1
+                    nocs = kk1 - kk0
                   }
                   if (length(nocs) > 0) {
                     spocum.t.dur.noc = sum(nocs)