diff --git a/CHANGES b/CHANGES
index 7fa5062a5d..13e625f3c3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,31 @@
+6.1.0-dev.538 | 2023-10-11 15:20:27 +0200
+
+  * ci/update-zeekygen-docs.sh: Do output stderr by default (Arne Welzel, Corelight)
+
+    stderr was only produced when there was a real failure as it had been a
+    bit noisy previously, but has hidden actual problems. Now that there is
+    less noise, just output stderr all the time.
+
+  * zeekygen: Disable zeek_init() handlers causing error output (Arne Welzel, Corelight)
+
+    These modules have zeek_init() handlers with actual logic that has side-effects
+    and error outputs. Just disable them during zeekygen runs.
+
+  * zeekygen/example: Squelch unused function warning (Arne Welzel, Corelight)
+
+  * iosource/pcap: Support configurable buffer size (Arne Welzel, Corelight)
+
+    On Linux with a default ext4 or tmpfs filesystem, the default buffer size for
+    reading a pcap is chosen as 4k (strace/gdb validated). When reading large pcaps
+    containing raw data transfers, the syscall overhead for read becomes visible
+    in profiles. Support configurability of the buffer size and default to 128kb.
+
+    When processing a ~830M PCAP (16 UDP connections, each transferring ~50MB) in
+    bare mode, this change improves runtime from 1.39 sec to 1.29 sec. Increasing
+    the buffer further didn't provide a noticeable boost.
+
+  * util/setvbuf: Respect buf argument (Arne Welzel, Corelight)
+
 6.1.0-dev.531 | 2023-10-11 14:09:22 +0200
 
   * protocol/ldap: Add doc-id/doc-description to .evt file (Arne Welzel, Corelight)
diff --git a/VERSION b/VERSION
index fa200f4eec..e649eeac10 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-6.1.0-dev.531
+6.1.0-dev.538
diff --git a/ci/update-zeekygen-docs.sh b/ci/update-zeekygen-docs.sh
index c4722237cb..278588752b 100755
--- a/ci/update-zeekygen-docs.sh
+++ b/ci/update-zeekygen-docs.sh
@@ -13,7 +13,6 @@ source_dir="$(cd $dir/.. && pwd)"
 build_dir=$source_dir/build
 conf_file=$build_dir/zeekygen-test.conf
 output_dir=$source_dir/doc
-zeek_error_file=$build_dir/zeekygen-test-stderr.txt
 
 if [ -n "$1" ]; then
     output_dir=$1
@@ -29,11 +28,10 @@ cd $build_dir
 export ZEEK_SEED_FILE=$source_dir/testing/btest/random.seed
 
 function run_zeek {
-    ZEEK_ALLOW_INIT_ERRORS=1 zeek -X $conf_file zeekygen >/dev/null 2>$zeek_error_file
+    ZEEK_ALLOW_INIT_ERRORS=1 zeek -X $conf_file zeekygen >/dev/null
 
     if [ $? -ne 0 ]; then
-        echo "Failed running zeek with zeekygen config file $conf_file"
-        echo "See stderr in $zeek_error_file"
+        echo "Failed running zeek with zeekygen config file $conf_file" >&2
         exit 1
     fi
 }
diff --git a/scripts/zeekygen/__load__.zeek b/scripts/zeekygen/__load__.zeek
index 2cfa93d48b..80a530bc3b 100644
--- a/scripts/zeekygen/__load__.zeek
+++ b/scripts/zeekygen/__load__.zeek
@@ -21,7 +21,14 @@
 
 @load ./example.zeek
 
-event zeek_init()
+event zeek_init() &priority=1000
 	{
+	# Disable events in modules that use zeek_init() to do stuff and may
+	# fail when run under zeekygen. For the purpose of zeekygen, we could
+	# probably disable all modules, too.
+	disable_module_events("Control");
+	disable_module_events("Management::Agent::Runtime");
+	disable_module_events("Management::Controller::Runtime");
+	disable_module_events("Management::Node");
 	terminate();
 	}
diff --git a/scripts/zeekygen/example.zeek b/scripts/zeekygen/example.zeek
index 360d044b64..681457d402 100644
--- a/scripts/zeekygen/example.zeek
+++ b/scripts/zeekygen/example.zeek
@@ -173,7 +173,7 @@ export {
 
 # This function isn't exported, so it won't appear anywhere in the generated
 # documentation.  So using ``##``-style comments is pointless here.
-function function_without_proto(tag: string): string
+function function_without_proto(tag: string): string &is_used
     {
     # Zeekygen-style comments only apply to entities at global-scope so
     # Zeekygen doesn't associate the following comments with anything.
diff --git a/testing/btest/Baseline/doc.zeekygen.identifier/test.rst b/testing/btest/Baseline/doc.zeekygen.identifier/test.rst
index 219c92da8b..b24dc870a3 100644
--- a/testing/btest/Baseline/doc.zeekygen.identifier/test.rst
+++ b/testing/btest/Baseline/doc.zeekygen.identifier/test.rst
@@ -240,6 +240,7 @@
    :source-code: zeekygen/example.zeek 176 184
 
    :Type: :zeek:type:`function` (tag: :zeek:type:`string`) : :zeek:type:`string`
+   :Attributes: :zeek:attr:`&is_used`
 
 
 .. zeek:type:: ZeekygenExample::PrivateRecord