diff --git a/docs/modernization/build-inventory.md b/docs/modernization/build-inventory.md
index 0f20605..acbaa83 100644
--- a/docs/modernization/build-inventory.md
+++ b/docs/modernization/build-inventory.md
@@ -92,7 +92,7 @@ Known local toolchain state:
   `pp_paint_renderer`,
   `pp_ui_core`, `pano_cli`, and their current headless test binaries,
   including foundation binary-stream/event/logging/task queue coverage, PNG metadata and
-  decode, PPI header/layout/non-finite opacity rejection, settings document, document
+  decode, PPI header/layout/non-finite opacity and blend-mode rejection, settings document, document
   snapshot/per-layer-frame/move/duration/face-pixel/PPI export coverage,
   snapshot-embedded face-payload rejection, paint brush/final-blend/
   stroke-alpha-blend/stroke spacing/stroke stress/stroke-script coverage,
diff --git a/docs/modernization/roadmap.md b/docs/modernization/roadmap.md
index d12e32e..209d615 100644
--- a/docs/modernization/roadmap.md
+++ b/docs/modernization/roadmap.md
@@ -316,7 +316,8 @@ PNG IHDR metadata parsing, PPI header/project byte-layout/body-summary
 recognition, layer/frame indexing, dirty-face PNG payload metadata validation,
 asset-level RGBA PNG payload decoding, and a pure typed settings document
 model, with
-corrupt/truncated/unsupported, non-finite opacity, extreme-dimension, and key/value limit tests.
+corrupt/truncated/unsupported, non-finite opacity, unsupported blend-mode,
+extreme-dimension, and key/value limit tests.
 `pp_paint` has started with pure brush parameter validation/stamp evaluation,
 CPU reference math for the five current final RGBA shader blend modes plus the
 shader-style stroke-alpha blend modes used by pattern/dual-brush mixing, and deterministic
diff --git a/src/assets/ppi_header.cpp b/src/assets/ppi_header.cpp
index 1270d36..830afe2 100644
--- a/src/assets/ppi_header.cpp
+++ b/src/assets/ppi_header.cpp
@@ -383,6 +383,11 @@ pp::foundation::Result<PpiBodySummary> parse_ppi_body_impl(
                     pp::foundation::Status::invalid_argument("PPI layer boolean field is invalid"));
             }
 
+            if (blend_mode.value() > 4U) {
+                return pp::foundation::Result<PpiBodySummary>::failure(
+                    pp::foundation::Status::out_of_range("PPI layer blend mode is outside the supported range"));
+            }
+
             if (index != nullptr) {
                 layer_summary.blend_mode = blend_mode.value();
                 layer_summary.alpha_locked = alpha_locked.value() != 0U;
diff --git a/tests/assets/ppi_header_tests.cpp b/tests/assets/ppi_header_tests.cpp
index 1481dbf..bb8fb67 100644
--- a/tests/assets/ppi_header_tests.cpp
+++ b/tests/assets/ppi_header_tests.cpp
@@ -395,10 +395,14 @@ void rejects_invalid_project_body_summaries(pp::tests::Harness& h)
         ppi_header_size + (128U * 128U * 4U) + 20U,
         std::numeric_limits<float>::quiet_NaN());
 
+    auto bad_blend_mode = minimal_project();
+    write_u32_at(bad_blend_mode, ppi_header_size + (128U * 128U * 4U) + 31U, 99U);
+
     const auto truncated_result = parse_ppi_project_summary(truncated);
     const auto mismatched_frames_result = parse_ppi_project_summary(mismatched_frames);
     const auto bad_layer_name_result = parse_ppi_project_summary(bad_layer_name);
     const auto non_finite_opacity_result = parse_ppi_project_summary(non_finite_opacity);
+    const auto bad_blend_mode_result = parse_ppi_project_summary(bad_blend_mode);
 
     PP_EXPECT(h, !truncated_result.ok());
     PP_EXPECT(h, truncated_result.status().code == StatusCode::out_of_range);
@@ -408,6 +412,8 @@ void rejects_invalid_project_body_summaries(pp::tests::Harness& h)
     PP_EXPECT(h, bad_layer_name_result.status().code == StatusCode::out_of_range);
     PP_EXPECT(h, !non_finite_opacity_result.ok());
     PP_EXPECT(h, non_finite_opacity_result.status().code == StatusCode::invalid_argument);
+    PP_EXPECT(h, !bad_blend_mode_result.ok());
+    PP_EXPECT(h, bad_blend_mode_result.status().code == StatusCode::out_of_range);
 }
 
 void creates_minimal_project_for_roundtrip_load(pp::tests::Harness& h)