diff --git a/tests/integration/run.bats b/tests/integration/run.bats
index e2eda270c..705868eb0 100644
--- a/tests/integration/run.bats
+++ b/tests/integration/run.bats
@@ -160,3 +160,73 @@ function teardown() {
 	[[ "$output" = *"Hello World"* ]]
 	[[ "$output" = *"runc-dmz: using /proc/self/exe clone"* ]]
 }
+
+@test "runc run [joining existing container namespaces]" {
+	requires timens
+
+	# Create a detached container with the namespaces we want. We notably want
+	# to include both userns and timens, which require config-related
+	# configuration.
+	if [ $EUID -eq 0 ]; then
+		update_config '.linux.namespaces += [{"type": "user"}]
+			| .linux.uidMappings += [{"containerID": 0, "hostID": 100000, "size": 100}]
+			| .linux.gidMappings += [{"containerID": 0, "hostID": 200000, "size": 200}]'
+		mkdir -p rootfs/{proc,sys,tmp}
+	fi
+	update_config '.linux.namespaces += [{"type": "time"}]
+		| .linux.timeOffsets = {
+			"monotonic": { "secs": 7881, "nanosecs": 2718281 },
+			"boottime": { "secs": 1337, "nanosecs": 3141519 }
+		}'
+	update_config '.process.args = ["sleep", "infinity"]'
+
+	runc run -d --console-socket "$CONSOLE_SOCKET" target_ctr
+	[ "$status" -eq 0 ]
+
+	# Modify our container's configuration such that it is just going to
+	# inherit all of the namespaces of the target container.
+	#
+	# NOTE: We cannot join the mount namespace of another container because of
+	# some quirks of the runtime-spec. In particular, we MUST pivot_root into
+	# root.path and root.path MUST be set in the config, so runc cannot just
+	# ignore root.path when joining namespaces (and root.path doesn't exist
+	# inside root.path, for obvious reasons).
+	#
+	# We could hack around this (create a copy of the rootfs inside the rootfs,
+	# or use a simpler mount namespace target), but those wouldn't be similar
+	# tests to the other namespace joining tests.
+	target_pid="$(__runc state target_ctr | jq .pid)"
+	update_config '.linux.namespaces |= map_values(.path = if .type == "mount" then "" else "/proc/'"$target_pid"'/ns/" + ({"network": "net", "mount": "mnt"}[.type] // .type) end)'
+	# Remove the userns and timens configuration (they cannot be changed).
+	update_config '.linux |= (del(.uidMappings) | del(.gidMappings) | del(.timeOffsets))'
+
+	runc run -d --console-socket "$CONSOLE_SOCKET" attached_ctr
+	[ "$status" -eq 0 ]
+
+	# Make sure there are two sleep processes in our container.
+	runc exec attached_ctr ps aux
+	[ "$status" -eq 0 ]
+	run -0 grep "sleep infinity" <<<"$output"
+	[ "${#lines[@]}" -eq 2 ]
+
+	# ... that the userns mappings are the same...
+	runc exec attached_ctr cat /proc/self/uid_map
+	[ "$status" -eq 0 ]
+	if [ $EUID -eq 0 ]; then
+		grep -E '^\s+0\s+100000\s+100$' <<<"$output"
+	else
+		grep -E '^\s+0\s+'$EUID'\s+1$' <<<"$output"
+	fi
+	runc exec attached_ctr cat /proc/self/gid_map
+	[ "$status" -eq 0 ]
+	if [ $EUID -eq 0 ]; then
+		grep -E '^\s+0\s+200000\s+200$' <<<"$output"
+	else
+		grep -E '^\s+0\s+'$EUID'\s+1$' <<<"$output"
+	fi
+
+	# ... as well as the timens offsets.
+	runc exec attached_ctr cat /proc/self/timens_offsets
+	grep -E '^monotonic\s+7881\s+2718281$' <<<"$output"
+	grep -E '^boottime\s+1337\s+3141519$' <<<"$output"
+}