diff --git a/libs/vkd3d-shader/hlsl_codegen.c b/libs/vkd3d-shader/hlsl_codegen.c
index 1c6d7748..b6ea5345 100644
--- a/libs/vkd3d-shader/hlsl_codegen.c
+++ b/libs/vkd3d-shader/hlsl_codegen.c
@@ -5331,6 +5331,7 @@ static void allocate_semantic_register(struct hlsl_ctx *ctx, struct hlsl_ir_var
 
     enum vkd3d_shader_register_type type;
     struct vkd3d_shader_version version;
+    bool special_interpolation = false;
     bool vip_allocation = false;
     uint32_t reg;
     bool builtin;
@@ -5389,6 +5390,9 @@ static void allocate_semantic_register(struct hlsl_ctx *ctx, struct hlsl_ir_var
                 || semantic == VKD3D_SHADER_SV_VIEWPORT_ARRAY_INDEX
                 || semantic == VKD3D_SHADER_SV_PRIMITIVE_ID)
             vip_allocation = true;
+
+        if (semantic == VKD3D_SHADER_SV_IS_FRONT_FACE || semantic == VKD3D_SHADER_SV_SAMPLE_INDEX)
+            special_interpolation = true;
     }
 
     if (builtin)
@@ -5402,6 +5406,9 @@ static void allocate_semantic_register(struct hlsl_ctx *ctx, struct hlsl_ir_var
                 ? 0 : sm4_get_interpolation_mode(var->data_type, var->storage_modifiers);
         unsigned int reg_size = optimize ? var->data_type->dimx : 4;
 
+        if (special_interpolation)
+            mode = VKD3DSIM_NONE;
+
         var->regs[HLSL_REGSET_NUMERIC] = allocate_register(ctx, allocator, 1, UINT_MAX,
                 reg_size, var->data_type->dimx, mode, var->force_align, vip_allocation);
 
diff --git a/tests/hlsl_d3d12.c b/tests/hlsl_d3d12.c
index ac07e802..51979a3b 100644
--- a/tests/hlsl_d3d12.c
+++ b/tests/hlsl_d3d12.c
@@ -2845,7 +2845,7 @@ static void test_signature_reflection(void)
         {vs6_source,  "vs_4_0", false, vs6_inputs, ARRAY_SIZE(vs6_inputs), vs6_outputs, ARRAY_SIZE(vs6_outputs)},
         {ps13_source, "ps_4_0", false, ps13_inputs, ARRAY_SIZE(ps13_inputs), ps_outputs_simple, ARRAY_SIZE(ps_outputs_simple)},
         {ps14_source, "ps_4_0", false, ps14_inputs, ARRAY_SIZE(ps14_inputs), ps_outputs_simple, ARRAY_SIZE(ps_outputs_simple)},
-        {ps15_source, "ps_4_1", false, ps15_inputs, ARRAY_SIZE(ps15_inputs), ps_outputs_simple, ARRAY_SIZE(ps_outputs_simple), NULL, 0, true},
+        {ps15_source, "ps_4_1", false, ps15_inputs, ARRAY_SIZE(ps15_inputs), ps_outputs_simple, ARRAY_SIZE(ps_outputs_simple)},
         {hs1_source,  "hs_5_0", false, NULL, 0, hs1_outputs, ARRAY_SIZE(hs1_outputs), hs1_patch_constants, ARRAY_SIZE(hs1_patch_constants)},
         {hs2_source,  "hs_5_0", false, NULL, 0, hs2_outputs, ARRAY_SIZE(hs2_outputs), hs2_patch_constants, ARRAY_SIZE(hs2_patch_constants)},
         {hs3_source,  "hs_5_0", false, NULL, 0, hs3_outputs, ARRAY_SIZE(hs3_outputs), hs3_patch_constants, ARRAY_SIZE(hs3_patch_constants)},