diff --git a/common/main/fwd-segment.h b/common/main/fwd-segment.h
index 211081d13..85b067b64 100644
--- a/common/main/fwd-segment.h
+++ b/common/main/fwd-segment.h
@@ -161,7 +161,8 @@ constexpr std::integral_constant<std::size_t, 32000> MAX_DELTA_LIGHTS{}; // Orig
 
 constexpr std::integral_constant<fix, 2048> DL_SCALE{};    // Divide light to allow 3 bits integer, 5 bits fraction.
 
-using d_delta_light_array = std::array<delta_light, MAX_DELTA_LIGHTS>;
+enum class delta_light_index : uint16_t;
+using d_delta_light_array = enumerated_array<delta_light, MAX_DELTA_LIGHTS, delta_light_index>;
 
 void clear_light_subtracted();
 
diff --git a/common/main/segment.h b/common/main/segment.h
index f2692aed2..9864991ed 100644
--- a/common/main/segment.h
+++ b/common/main/segment.h
@@ -396,6 +396,10 @@ struct shared_side::illegal_type : std::runtime_error
 namespace dsx {
 
 #if defined(DXX_BUILD_DESCENT_II)
+enum class delta_light_index : uint16_t
+{
+};
+
 // New stuff, 10/14/95: For shooting out lights and monitors.
 // Light cast upon vert_light vertices in segnum:sidenum by some light
 struct delta_light : prohibit_void_ptr<delta_light>
@@ -410,7 +414,7 @@ struct dl_index {
 	segnum_t   segnum;
 	sidenum_t  sidenum;
 	uint8_t count;
-	uint16_t index;
+	delta_light_index index;
 	constexpr std::strong_ordering operator<=>(const dl_index &rhs) const
 	{
 		if (const auto r = segnum <=> rhs.segnum; r != std::strong_ordering::equal)
diff --git a/similar/main/gameseg.cpp b/similar/main/gameseg.cpp
index a6e52339f..629cc2de3 100644
--- a/similar/main/gameseg.cpp
+++ b/similar/main/gameseg.cpp
@@ -1733,12 +1733,12 @@ static void change_light(const d_level_shared_destructible_light_state &LevelSha
 	const fix ds = dir * DL_SCALE;
 	auto &Dl_indices = LevelSharedDestructibleLightState.Dl_indices;
 	const auto &&pr = cast_range_result<const dl_index &>(Dl_indices.vcptr);
-	const auto &&er = std::equal_range(pr.begin(), pr.end(), dl_index{segnum, sidenum, 0, 0});
+	const auto &&er = std::equal_range(pr.begin(), pr.end(), dl_index{segnum, sidenum, 0, {}});
 	auto &Delta_lights = LevelSharedDestructibleLightState.Delta_lights;
 	range_for (auto &i, partial_range_t<const dl_index *>(er.first.base().base(), er.second.base().base()))
 	{
-		const uint_fast32_t idx = i.index;
-			range_for (auto &j, partial_const_range(Delta_lights, idx, idx + i.count))
+		const std::size_t idx = underlying_value(i.index);
+		for (auto &j : partial_const_range(Delta_lights, idx, idx + i.count))
 			{
 				assert(j.sidenum < MAX_SIDES_PER_SEGMENT);
 				const auto &&segp = vmsegptr(j.segnum);
diff --git a/similar/main/segment.cpp b/similar/main/segment.cpp
index 1c18be99d..f93409d30 100644
--- a/similar/main/segment.cpp
+++ b/similar/main/segment.cpp
@@ -58,6 +58,14 @@ void segment_side_wall_tmap_write(PHYSFS_File *fp, const shared_side &sside, con
 #if defined(DXX_BUILD_DESCENT_II)
 namespace dsx {
 
+static std::optional<delta_light_index> build_delta_light_index_from_untrusted(const uint16_t i)
+{
+	if (i < MAX_DELTA_LIGHTS)
+		return delta_light_index{i};
+	else
+		return std::nullopt;
+}
+
 /*
  * reads a delta_light structure from a PHYSFS_File
  */
@@ -86,8 +94,17 @@ void dl_index_read(dl_index *di, PHYSFS_File *fp)
 		di->segnum = vmsegidx_t::check_nothrow_index(s) ? s : segment_none;
 	}
 	di->sidenum = build_sidenum_from_untrusted(PHYSFSX_readByte(fp)).value_or(sidenum_t::WLEFT);
-	di->count = PHYSFSX_readByte(fp);
-	di->index = PHYSFSX_readShort(fp);
+	const auto count = PHYSFSX_readByte(fp);
+	if (const auto i = build_delta_light_index_from_untrusted(PHYSFSX_readShort(fp)); i)
+	{
+		di->count = count;
+		di->index = *i;
+	}
+	else
+	{
+		di->count = 0;
+		di->index = {};
+	}
 }
 
 void segment2_write(const cscusegment s2, PHYSFS_File *fp)
@@ -115,7 +132,7 @@ void dl_index_write(const dl_index *di, PHYSFS_File *fp)
 	PHYSFS_writeSLE16(fp, di->segnum);
 	PHYSFSX_writeU8(fp, underlying_value(di->sidenum));
 	PHYSFSX_writeU8(fp, di->count);
-	PHYSFS_writeSLE16(fp, di->index);
+	PHYSFS_writeSLE16(fp, underlying_value(di->index));
 }
 
 }