diff --git a/src/Common/Game/IW4/IW4_Assets.h b/src/Common/Game/IW4/IW4_Assets.h
index 471d7efe..75f4c755 100644
--- a/src/Common/Game/IW4/IW4_Assets.h
+++ b/src/Common/Game/IW4/IW4_Assets.h
@@ -950,6 +950,15 @@ namespace IW4
         TEXTURE_SRC_CODE_COUNT
     };
 
+    enum CustomSamplers
+    {
+        CUSTOM_SAMPLER_REFLECTION_PROBE = 0x0,
+        CUSTOM_SAMPLER_LIGHTMAP_PRIMARY = 0x1,
+        CUSTOM_SAMPLER_LIGHTMAP_SECONDARY = 0x2,
+
+        CUSTOM_SAMPLER_COUNT
+    };
+
     struct CodeSamplerSource
     {
         const char* name;
diff --git a/src/ObjCommon/Game/IW4/TechsetConstantsIW4.h b/src/ObjCommon/Game/IW4/TechsetConstantsIW4.h
index ce281988..c8f5069e 100644
--- a/src/ObjCommon/Game/IW4/TechsetConstantsIW4.h
+++ b/src/ObjCommon/Game/IW4/TechsetConstantsIW4.h
@@ -507,6 +507,14 @@ namespace IW4
     };
     static_assert(std::extent_v<decltype(s_codeSamplerUpdateFreq)> == TEXTURE_SRC_CODE_COUNT);
 
+    inline MaterialTextureSource g_customSamplerSrc[]
+    {
+        TEXTURE_SRC_CODE_REFLECTION_PROBE, // CUSTOM_SAMPLER_REFLECTION_PROBE
+        TEXTURE_SRC_CODE_LIGHTMAP_PRIMARY, // CUSTOM_SAMPLER_LIGHTMAP_PRIMARY
+        TEXTURE_SRC_CODE_LIGHTMAP_SECONDARY // CUSTOM_SAMPLER_LIGHTMAP_SECONDARY
+    };
+    static_assert(std::extent_v<decltype(g_customSamplerSrc)> == CUSTOM_SAMPLER_COUNT);
+
     static constexpr std::pair<uint32_t, const char*> KnownMaterialSource(const char* name)
     {
         return std::make_pair(Common::R_HashString(name, 0u), name);
diff --git a/src/ObjLoading/Game/IW4/AssetLoaders/AssetLoaderTechniqueSet.cpp b/src/ObjLoading/Game/IW4/AssetLoaders/AssetLoaderTechniqueSet.cpp
index b4319f90..95e64030 100644
--- a/src/ObjLoading/Game/IW4/AssetLoaders/AssetLoaderTechniqueSet.cpp
+++ b/src/ObjLoading/Game/IW4/AssetLoaders/AssetLoaderTechniqueSet.cpp
@@ -131,7 +131,7 @@ namespace IW4
 
             static MaterialUpdateFrequency GetUpdateFrequencyForArg(MaterialShaderArgument arg)
             {
-                switch(arg.type)
+                switch (arg.type)
                 {
                 case MTL_ARG_CODE_VERTEX_CONST:
                 case MTL_ARG_CODE_PIXEL_CONST:
@@ -143,7 +143,7 @@ namespace IW4
                     return s_codeConstUpdateFreq[arg.u.codeConst.index];
 
                 case MTL_ARG_CODE_PIXEL_SAMPLER:
-                    if(arg.u.codeSampler >= std::extent_v<decltype(s_codeSamplerUpdateFreq)>)
+                    if (arg.u.codeSampler >= std::extent_v<decltype(s_codeSamplerUpdateFreq)>)
                     {
                         assert(false);
                         return MTL_UPDATE_RARELY;
@@ -1011,9 +1011,23 @@ namespace IW4
                     stableArgCount++;
                     break;
                 case MTL_UPDATE_CUSTOM:
+                    {
+                        assert(arg.m_arg.type == MTL_ARG_CODE_PIXEL_SAMPLER);
+                        if (arg.m_arg.type == MTL_ARG_CODE_PIXEL_SAMPLER)
+                        {
+                            const auto customSampler = std::find(std::begin(g_customSamplerSrc), std::end(g_customSamplerSrc), arg.m_arg.u.codeSampler);
+                            assert(customSampler != std::end(g_customSamplerSrc));
+                            if (customSampler != std::end(g_customSamplerSrc))
+                            {
+                                const auto customSamplerIndex = customSampler - std::begin(g_customSamplerSrc);
+                                out.customSamplerFlags |= 1 << customSamplerIndex;
+                            }
+                        }
+                    }
+                    continue;
                 default:
                     assert(false);
-                    break;
+                    continue;
                 }
 
                 out.args[argIndex++] = arg.m_arg;