diff --git a/core/src/main/kotlin/net/corda/core/internal/PlatformVersionSwitches.kt b/core/src/main/kotlin/net/corda/core/internal/PlatformVersionSwitches.kt
index f40ea96c6c..e32044ac02 100644
--- a/core/src/main/kotlin/net/corda/core/internal/PlatformVersionSwitches.kt
+++ b/core/src/main/kotlin/net/corda/core/internal/PlatformVersionSwitches.kt
@@ -19,4 +19,6 @@ object PlatformVersionSwitches {
     const val RESTRICTED_DATABASE_OPERATIONS = 7
     const val CERTIFICATE_ROTATION = 9
     const val TWO_PHASE_FINALITY = 13
+    const val LEGACY_ATTACHMENTS = 140
+
 }
\ No newline at end of file
diff --git a/core/src/main/kotlin/net/corda/core/internal/cordapp/CordappProviderInternal.kt b/core/src/main/kotlin/net/corda/core/internal/cordapp/CordappProviderInternal.kt
index fd83ba26f1..a3e6036370 100644
--- a/core/src/main/kotlin/net/corda/core/internal/cordapp/CordappProviderInternal.kt
+++ b/core/src/main/kotlin/net/corda/core/internal/cordapp/CordappProviderInternal.kt
@@ -17,7 +17,7 @@ interface CordappProviderInternal : CordappProvider {
      * Similar to [getContractAttachmentID] except it returns the [ContractAttachment] object and also returns an optional second attachment
      * representing the legacy version (4.11 or earlier) of the contract, if one exists.
      */
-    fun getContractAttachments(contractClassName: ContractClassName): ContractAttachmentWithLegacy?
+    fun getContractAttachments(contractClassName: ContractClassName, minimumPlatformVersion: Int): ContractAttachmentWithLegacy?
 }
 
 data class ContractAttachmentWithLegacy(val currentAttachment: ContractAttachment, val legacyAttachment: ContractAttachment? = null)
diff --git a/core/src/main/kotlin/net/corda/core/transactions/TransactionBuilder.kt b/core/src/main/kotlin/net/corda/core/transactions/TransactionBuilder.kt
index d954abda92..221a31cc84 100644
--- a/core/src/main/kotlin/net/corda/core/transactions/TransactionBuilder.kt
+++ b/core/src/main/kotlin/net/corda/core/transactions/TransactionBuilder.kt
@@ -695,10 +695,10 @@ open class TransactionBuilder(
             contractClassName: String,
             statesForException: () -> List<TransactionState<*>>
     ): ContractAttachmentWithLegacy {
-        // TODO Stop using legacy attachments when the 4.12 min platform version is reached https://r3-cev.atlassian.net/browse/ENT-11479
-        val attachmentWithLegacy = cordappProvider.getContractAttachments(contractClassName)
+        // Stop using legacy attachments when the 4.12 min platform version is reached
+        val attachmentWithLegacy = cordappProvider.getContractAttachments(contractClassName, networkParameters.minimumPlatformVersion)
                 ?: throw MissingContractAttachments(statesForException(), contractClassName)
-        if (attachmentWithLegacy.legacyAttachment == null) {
+        if (networkParameters.minimumPlatformVersion < PlatformVersionSwitches.LEGACY_ATTACHMENTS && attachmentWithLegacy.legacyAttachment == null) {
             log.warnOnce("Contract $contractClassName does not have a legacy (4.11 or earlier) version installed. This means the " +
                     "transaction will not be compatible with older nodes.")
         }
diff --git a/node/src/main/kotlin/net/corda/node/internal/cordapp/CordappProviderImpl.kt b/node/src/main/kotlin/net/corda/node/internal/cordapp/CordappProviderImpl.kt
index 60e6483074..c11aa324c4 100644
--- a/node/src/main/kotlin/net/corda/node/internal/cordapp/CordappProviderImpl.kt
+++ b/node/src/main/kotlin/net/corda/node/internal/cordapp/CordappProviderImpl.kt
@@ -6,6 +6,7 @@ import net.corda.core.cordapp.Cordapp
 import net.corda.core.cordapp.CordappContext
 import net.corda.core.flows.FlowLogic
 import net.corda.core.internal.DEPLOYED_CORDAPP_UPLOADER
+import net.corda.core.internal.PlatformVersionSwitches
 import net.corda.core.internal.cordapp.ContractAttachmentWithLegacy
 import net.corda.core.internal.cordapp.CordappImpl
 import net.corda.core.internal.cordapp.CordappProviderInternal
@@ -61,9 +62,10 @@ open class CordappProviderImpl(private val cordappLoader: CordappLoader,
         return cordappLoader.cordapps.findCordapp(contractClassName)
     }
 
-    override fun getContractAttachments(contractClassName: ContractClassName): ContractAttachmentWithLegacy? {
+    override fun getContractAttachments(contractClassName: ContractClassName, minimumPlatformVersion: Int): ContractAttachmentWithLegacy? {
         val currentAttachmentId = getContractAttachmentID(contractClassName) ?: return null
-        val legacyAttachmentId = cordappLoader.legacyContractCordapps.findCordapp(contractClassName)
+        val legacyAttachmentId = if (minimumPlatformVersion < PlatformVersionSwitches.LEGACY_ATTACHMENTS)
+            cordappLoader.legacyContractCordapps.findCordapp(contractClassName) else null
         return ContractAttachmentWithLegacy(getContractAttachment(currentAttachmentId), legacyAttachmentId?.let(::getContractAttachment))
     }
 
diff --git a/node/src/test/kotlin/net/corda/node/internal/cordapp/CordappProviderImplTests.kt b/node/src/test/kotlin/net/corda/node/internal/cordapp/CordappProviderImplTests.kt
index 88942ca7cc..395e10bcf5 100644
--- a/node/src/test/kotlin/net/corda/node/internal/cordapp/CordappProviderImplTests.kt
+++ b/node/src/test/kotlin/net/corda/node/internal/cordapp/CordappProviderImplTests.kt
@@ -2,6 +2,7 @@ package net.corda.node.internal.cordapp
 
 import com.typesafe.config.Config
 import com.typesafe.config.ConfigFactory
+import net.corda.core.internal.PlatformVersionSwitches
 import net.corda.core.internal.hash
 import net.corda.core.internal.toPath
 import net.corda.core.node.services.AttachmentId
@@ -134,9 +135,19 @@ class CordappProviderImplTests {
     }
 
     @Test(timeout=300_000)
-    fun `retrieving legacy attachment for contract`() {
+    fun `retrieving legacy attachment for contract on network that does not support pre-412 `() {
         val provider = newCordappProvider(setOf(currentFinanceContractsJar), setOf(legacyFinanceContractsJar))
-        val (current, legacy) = provider.getContractAttachments(Cash::class.java.name)!!
+        val (current, legacy) = provider.getContractAttachments(Cash::class.java.name, PlatformVersionSwitches.LEGACY_ATTACHMENTS)!!
+        assertThat(current.id).isEqualTo(currentFinanceContractsJar.hash)
+        assertThat(legacy?.id).isNull()
+        // getContractAttachmentID should always return the non-legacy attachment ID
+        assertThat(provider.getContractAttachmentID(Cash::class.java.name)).isEqualTo(currentFinanceContractsJar.hash)
+    }
+
+    @Test(timeout = 300_000)
+    fun `retrieving legacy attachment for contract on mixed network of versions`() {
+        val provider = newCordappProvider(setOf(currentFinanceContractsJar), setOf(legacyFinanceContractsJar))
+        val (current, legacy) = provider.getContractAttachments(Cash::class.java.name, PlatformVersionSwitches.LEGACY_ATTACHMENTS - 1)!!
         assertThat(current.id).isEqualTo(currentFinanceContractsJar.hash)
         assertThat(legacy?.id).isEqualTo(legacyFinanceContractsJar.hash)
         // getContractAttachmentID should always return the non-legacy attachment ID