diff --git a/src/main/kotlin/protocols/RatesFixProtocol.kt b/src/main/kotlin/protocols/RatesFixProtocol.kt
index 227b0a8b34..ad955983d8 100644
--- a/src/main/kotlin/protocols/RatesFixProtocol.kt
+++ b/src/main/kotlin/protocols/RatesFixProtocol.kt
@@ -27,11 +27,11 @@ import java.util.*
  *
  * @throws FixOutOfRange if the returned fix was further away from the expected rate by the given amount.
  */
-class RatesFixProtocol(private val tx: TransactionBuilder,
-                       private val oracle: LegallyIdentifiableNode,
-                       private val fixOf: FixOf,
-                       private val expectedRate: BigDecimal,
-                       private val rateTolerance: BigDecimal) : ProtocolLogic<Unit>() {
+open class RatesFixProtocol(protected val tx: TransactionBuilder,
+                            private val oracle: LegallyIdentifiableNode,
+                            private val fixOf: FixOf,
+                            private val expectedRate: BigDecimal,
+                            private val rateTolerance: BigDecimal) : ProtocolLogic<Unit>() {
     companion object {
         val TOPIC = "platform.rates.interest.fix"
     }
@@ -46,9 +46,18 @@ class RatesFixProtocol(private val tx: TransactionBuilder,
         val fix = query()
         checkFixIsNearExpected(fix)
         tx.addCommand(fix, oracle.identity.owningKey)
+        beforeSigning(fix)
         tx.addSignatureUnchecked(sign())
     }
 
+    /**
+     * You can override this to perform any additional work needed after the fix is added to the transaction but
+     * before it's sent back to the oracle for signing (for example, adding output states that depend on the fix).
+     */
+    @Suspendable
+    protected open fun beforeSigning(fix: Fix) {
+    }
+
     private fun checkFixIsNearExpected(fix: Fix) {
         val delta = (fix.value - expectedRate).abs()
         if (delta > rateTolerance) {