diff --git a/src/main/java/net/fabricmc/loom/util/fmj/FabricModJson.java b/src/main/java/net/fabricmc/loom/util/fmj/FabricModJson.java
index 96dbd9e1..5e5cc379 100644
--- a/src/main/java/net/fabricmc/loom/util/fmj/FabricModJson.java
+++ b/src/main/java/net/fabricmc/loom/util/fmj/FabricModJson.java
@@ -67,7 +67,7 @@ public abstract sealed class FabricModJson permits FabricModJsonV0, FabricModJso
 	}
 
 	@Override
-	public int hashCode() {
+	public final int hashCode() {
 		return Objects.hash(getId(), getVersion());
 	}
 
diff --git a/src/main/java/net/fabricmc/loom/util/fmj/ModMetadataFabricModJson.java b/src/main/java/net/fabricmc/loom/util/fmj/ModMetadataFabricModJson.java
index 46de0b36..a60f6a4e 100644
--- a/src/main/java/net/fabricmc/loom/util/fmj/ModMetadataFabricModJson.java
+++ b/src/main/java/net/fabricmc/loom/util/fmj/ModMetadataFabricModJson.java
@@ -42,6 +42,7 @@ import org.jetbrains.annotations.Nullable;
 import net.fabricmc.loom.util.gradle.SourceSetHelper;
 
 public final class ModMetadataFabricModJson extends FabricModJson {
+	private static final int FABRIC_SCHEMA_VERSION = -1;
 	private final ModMetadataFile modMetadata;
 	private final FabricModJsonSource source;
 
@@ -99,7 +100,9 @@ public final class ModMetadataFabricModJson extends FabricModJson {
 
 	@Override
 	public int getVersion() {
-		throw new UnsupportedOperationException();
+		// Technically not correct since we're not a real fabric.mod.json,
+		// but this is needed for computing the hash code.
+		return FABRIC_SCHEMA_VERSION;
 	}
 
 	@Override
@@ -122,9 +125,4 @@ public final class ModMetadataFabricModJson extends FabricModJson {
 				.stream()
 				.collect(Collectors.toMap(Function.identity(), path -> ModEnvironment.UNIVERSAL));
 	}
-
-	@Override
-	public int hashCode() {
-		return modMetadata.hashCode();
-	}
 }