diff --git a/case-lib/hijack.sh b/case-lib/hijack.sh
index f7bd67b0..ead9f31b 100644
--- a/case-lib/hijack.sh
+++ b/case-lib/hijack.sh
@@ -86,6 +86,8 @@ function func_exit_handler()
     fi
 
     if [[ "$KERNEL_CHECKPOINT" =~ ^[0-9]{10} ]]; then
+        # Do not collect the entire duration of the test but only the
+        # last iteration.
         journalctl_cmd --since=@"$KERNEL_CHECKPOINT" > "$LOG_ROOT/dmesg.txt"
     elif [[ "$KERNEL_CHECKPOINT" == "disabled" ]]; then
         journalctl_cmd > "$LOG_ROOT/dmesg.txt"
diff --git a/case-lib/lib.sh b/case-lib/lib.sh
index 2798ae56..cfcdf604 100644
--- a/case-lib/lib.sh
+++ b/case-lib/lib.sh
@@ -82,7 +82,14 @@ setup_kernel_check_point()
     # appear in the next one, see comments in config.sh.  Add 3 extra
     # second to account for our own, sof-test delays after PASS/FAIL
     # decision: time spent collecting logs etc.
-    KERNEL_CHECKPOINT=$(($(date +%s) - SOF_TEST_INTERVAL - 3))
+    if [ -z "$KERNEL_CHECKPOINT" ]; then
+        KERNEL_CHECKPOINT=$(($(date +%s) - SOF_TEST_INTERVAL - 3))
+    else
+        # Not the first time we are called so this is a test
+        # _iteration_. Add just one extra second in case a test makes
+        # the mistake to call this function _after_ checking the logs.
+        KERNEL_CHECKPOINT=$(($(date +%s) - 1))
+    fi
 }
 
 # This function adds a fake error to dmesg (which is always saved by
@@ -425,6 +432,8 @@ journalctl_cmd()
      --no-hostname "$@"
 }
 
+# Force the exit handler to collect all the logs since boot time instead
+# of just the last test iteration.
 disable_kernel_check_point()
 {
     KERNEL_CHECKPOINT="disabled"
diff --git a/tools/sof-kernel-log-check.sh b/tools/sof-kernel-log-check.sh
index ffa1c0d1..131d807e 100755
--- a/tools/sof-kernel-log-check.sh
+++ b/tools/sof-kernel-log-check.sh
@@ -126,7 +126,11 @@
 # Append some garbage to an ignore pattern to turn it off. Much easier
 # than deleting it.
 
-begin_timestamp=${1:-0}
+# Don't look at journalctl logs before this time in seconds since
+# 1970. Defaults to zero which is a no-op because we always use -k or
+# -b.
+begin_timestamp=${1:-0000000000}
+
 declare ignore_str
 
 # pwd resolves relative paths
@@ -376,7 +380,7 @@ ignore_str="$ignore_str"'|iwlwifi [[:digit:].:]+: '
 if [[ $begin_timestamp =~ ^[0-9]{10} ]]; then
     cmd="journalctl_cmd --since=@$begin_timestamp"
 else
-    cmd="journalctl_cmd"
+    die "Invalid begin_timestamp $1 argument: $begin_timestamp"
 fi
 
 declare -p cmd
@@ -388,6 +392,7 @@ else
 fi
 
 [[ -z "$err" ]] || {
+    type journalctl_cmd
     echo "$(date -u '+%Y-%m-%d %T %Z')" "[ERROR]" "Caught kernel log error"
     echo "===========================>>"
     echo "$err"