diff --git a/application/src/main/java/net/corda/v5/application/interop/parameters/ParameterTypeLabel.java b/application/src/main/java/net/corda/v5/application/interop/parameters/ParameterTypeLabel.java
index 57830c4562..43a23acf6b 100644
--- a/application/src/main/java/net/corda/v5/application/interop/parameters/ParameterTypeLabel.java
+++ b/application/src/main/java/net/corda/v5/application/interop/parameters/ParameterTypeLabel.java
@@ -1,5 +1,6 @@
 package net.corda.v5.application.interop.parameters;
 
+import net.corda.v5.application.crypto.DigitalSignatureAndMetadata;
 import org.jetbrains.annotations.NotNull;
 import java.math.BigDecimal;
 import java.nio.ByteBuffer;
@@ -16,7 +17,8 @@ public enum ParameterTypeLabel {
     UUID(java.util.UUID.class),
     TIMESTAMP(ZonedDateTime.class),
     BYTES(ByteBuffer.class),
-    JSON(String.class);
+    JSON(String.class),
+    SIGNED_TX(DigitalSignatureAndMetadata.class);
 
     @NotNull
     private final Class<?> expectedClass;
diff --git a/application/src/main/java/net/corda/v5/application/marshalling/InteropJsonMarshallingService.java b/application/src/main/java/net/corda/v5/application/marshalling/InteropJsonMarshallingService.java
new file mode 100644
index 0000000000..4a865cdac6
--- /dev/null
+++ b/application/src/main/java/net/corda/v5/application/marshalling/InteropJsonMarshallingService.java
@@ -0,0 +1,16 @@
+package net.corda.v5.application.marshalling;
+
+import net.corda.v5.application.flows.ClientStartableFlow;
+import net.corda.v5.base.annotations.DoNotImplement;
+
+/**
+ * {@link InteropJsonMarshallingService} marshalls to and from JSON using the registered JSON mapper.
+ * <p>
+ * The platform will provide an instance of {@link InteropJsonMarshallingService} to flows via property injection.
+ * <p>
+ * Example usage:
+ * @see ClientStartableFlow
+ */
+@DoNotImplement
+public interface InteropJsonMarshallingService extends MarshallingService {
+}
diff --git a/gradle.properties b/gradle.properties
index b9a08da1fd..43b5041d18 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -12,7 +12,7 @@ cordaProductVersion = 5.1.0-INTEROP
 ## IMPORTANT:
 ## The interop feature branches track api revisions separately to the mainline branch.
 ## API version of last merge from corda mainline: 32
-cordaApiRevision = 24
+cordaApiRevision = 25
 
 # Main
 kotlinVersion = 1.8.21