diff --git a/src/test/fixtures/README.md b/src/test/fixtures/README.md
index bc85103..41d956d 100644
--- a/src/test/fixtures/README.md
+++ b/src/test/fixtures/README.md
@@ -47,3 +47,14 @@ Compiled with Scala 2.11.5 under Java 8, `-target:jvm-1.8`, against the referenc
 (SHA-256 `da0a35a968905203187edc5a1f26018305cf146114426ed7b468080b40c95771`). Class-file SHA-256 is
 `0ce8ddd700df8ec859325133a1a683de1aceaabd67cb4c0d1867e6cb907e5790`, stored as
 `src/test/resources/compat/ReferenceScalaNormalOcclusion.class.b64`.
+
+### `ReferenceScalaFacePart`
+
+`scala/codechicken/multipart/compat/ReferenceScalaFacePart.scala` mixes in `TFacePart` without overriding either
+member it supplies, so its compiled forwarders call all three `TFacePart$class` statics: `solid`,
+`redstoneConductionMap` and `$init$`. OpenComputers, ProjRed and ProjectBlue depend on those descriptors.
+
+Compiled with Scala 2.11.5 under Java 8, `-target:jvm-1.8`, against the reference dev jar built at `a1bf3c8`
+(SHA-256 `1cb57d8728f06b3d283b0bca8ce9f92a58f4c2b8cc835fa4f7ee3de6338c27ec`). Class-file SHA-256 is
+`a95dfa131f57e6e6efdba25e989154899d9b1f9a5cbff7a1e6b4374ec9c2b0b2`, stored as
+`src/test/resources/compat/ReferenceScalaFacePart.class.b64`.
diff --git a/src/test/fixtures/scala/codechicken/multipart/compat/ReferenceScalaFacePart.scala b/src/test/fixtures/scala/codechicken/multipart/compat/ReferenceScalaFacePart.scala
new file mode 100644
index 0000000..f34a625
--- /dev/null
+++ b/src/test/fixtures/scala/codechicken/multipart/compat/ReferenceScalaFacePart.scala
@@ -0,0 +1,12 @@
+package codechicken.multipart.compat
+
+import codechicken.multipart.{TFacePart, TMultiPart}
+
+/** Mixes in TFacePart without overriding either supplied member, so the compiled forwarders call
+  * TFacePart$class.solid, TFacePart$class.redstoneConductionMap and TFacePart$class.$init$.
+  */
+class ReferenceScalaFacePart extends TMultiPart with TFacePart {
+  def getType = "test:reference-face"
+
+  def getSlotMask = 0x3f
+}
diff --git a/src/test/java/codechicken/multipart/FacePartCharacterizationTest.java b/src/test/java/codechicken/multipart/FacePartCharacterizationTest.java
new file mode 100644
index 0000000..1d06b83
--- /dev/null
+++ b/src/test/java/codechicken/multipart/FacePartCharacterizationTest.java
@@ -0,0 +1,88 @@
+package codechicken.multipart;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class FacePartCharacterizationTest {
+
+    @Test
+    void defaultsAreSolidOnEverySideAndConductNothing() {
+        ForwardingPart part = new ForwardingPart();
+
+        for (int side = 0; side < 6; side++) {
+            assertTrue(part.solid(side));
+        }
+        assertTrue(part.solid(-1));
+        assertTrue(part.solid(99));
+        assertEquals(0, part.redstoneConductionMap());
+    }
+
+    @Test
+    void deprecatedBridgeMatchesTheDefaults() {
+        ForwardingPart part = new ForwardingPart();
+
+        for (int side = 0; side < 6; side++) {
+            assertTrue(TFacePart$class.solid(part, side));
+        }
+        assertEquals(0, TFacePart$class.redstoneConductionMap(part));
+    }
+
+    /** The bridge holds the trait defaults rather than dispatching, so an override does not change what it returns. */
+    @Test
+    void deprecatedBridgeReturnsTheTraitDefaultsEvenWhenOverridden() {
+        OverridingPart part = new OverridingPart();
+
+        assertFalse(part.solid(0));
+        assertEquals(0x10, part.redstoneConductionMap());
+        assertTrue(TFacePart$class.solid(part, 0));
+        assertEquals(0, TFacePart$class.redstoneConductionMap(part));
+    }
+
+    @Test
+    void facePartIsASlottedPart() {
+        ForwardingPart part = new ForwardingPart();
+
+        assertTrue(part instanceof TSlottedPart);
+        assertEquals(0x3f, part.getSlotMask());
+    }
+
+    /** Mirrors the forwarders Scala emits for a class mixing in the trait without overriding either member. */
+    private static class ForwardingPart extends TMultiPart implements TFacePart {
+
+        @Override
+        public String getType() {
+            return "test:face";
+        }
+
+        @Override
+        public int getSlotMask() {
+            return 0x3f;
+        }
+
+        @Override
+        public boolean solid(int side) {
+            return TFacePart$class.solid(this, side);
+        }
+
+        @Override
+        public int redstoneConductionMap() {
+            return TFacePart$class.redstoneConductionMap(this);
+        }
+    }
+
+    private static final class OverridingPart extends ForwardingPart {
+
+        @Override
+        public boolean solid(int side) {
+            return false;
+        }
+
+        @Override
+        public int redstoneConductionMap() {
+            return 0x10;
+        }
+    }
+}
diff --git a/src/test/java/codechicken/multipart/TFacePartBinaryCompatibilityTest.java b/src/test/java/codechicken/multipart/TFacePartBinaryCompatibilityTest.java
new file mode 100644
index 0000000..6a99073
--- /dev/null
+++ b/src/test/java/codechicken/multipart/TFacePartBinaryCompatibilityTest.java
@@ -0,0 +1,55 @@
+package codechicken.multipart;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+import java.util.Objects;
+import java.util.Scanner;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Loads a Scala class compiled against the reference dev jar, whose forwarders call all three TFacePart$class statics.
+ * Recompiling the fixture against the port would hide the linkage failure this exists to catch.
+ */
+class TFacePartBinaryCompatibilityTest {
+
+    @Test
+    void referenceScalaImplementorStillLinksThroughTheBridge() throws Exception {
+        Class<?> fixtureClass = new FixtureClassLoader(TFacePart.class.getClassLoader()).define(loadFixture());
+        Object fixture = fixtureClass.getDeclaredConstructor().newInstance();
+
+        assertTrue(fixture instanceof TFacePart);
+        assertTrue(fixture instanceof TSlottedPart);
+        assertTrue(fixture instanceof TMultiPart);
+        TFacePart part = (TFacePart) fixture;
+
+        for (int side = 0; side < 6; side++) {
+            assertTrue(part.solid(side));
+        }
+        assertEquals(0, part.redstoneConductionMap());
+        assertEquals(0x3f, part.getSlotMask());
+    }
+
+    private static byte[] loadFixture() {
+        InputStream input = Objects.requireNonNull(
+                TFacePartBinaryCompatibilityTest.class.getResourceAsStream("/compat/ReferenceScalaFacePart.class.b64"));
+        try (Scanner scanner = new Scanner(input, StandardCharsets.US_ASCII.name()).useDelimiter("\\A")) {
+            return Base64.getMimeDecoder().decode(scanner.next());
+        }
+    }
+
+    private static final class FixtureClassLoader extends ClassLoader {
+
+        private FixtureClassLoader(ClassLoader parent) {
+            super(parent);
+        }
+
+        private Class<?> define(byte[] bytecode) {
+            return defineClass(null, bytecode, 0, bytecode.length);
+        }
+    }
+}
diff --git a/src/test/resources/compat/ReferenceScalaFacePart.class.b64 b/src/test/resources/compat/ReferenceScalaFacePart.class.b64
new file mode 100644
index 0000000..598030c
--- /dev/null
+++ b/src/test/resources/compat/ReferenceScalaFacePart.class.b64
@@ -0,0 +1,25 @@
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