diff --git a/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraints.kt b/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraints.kt
index 08c7e487b57..78d6078b05a 100644
--- a/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraints.kt
+++ b/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraints.kt
@@ -10,7 +10,9 @@ import software.amazon.smithy.model.shapes.BlobShape
 import software.amazon.smithy.model.shapes.ByteShape
 import software.amazon.smithy.model.shapes.EnumShape
 import software.amazon.smithy.model.shapes.IntegerShape
+import software.amazon.smithy.model.shapes.ListShape
 import software.amazon.smithy.model.shapes.LongShape
+import software.amazon.smithy.model.shapes.MapShape
 import software.amazon.smithy.model.shapes.MemberShape
 import software.amazon.smithy.model.shapes.OperationShape
 import software.amazon.smithy.model.shapes.ServiceShape
@@ -36,13 +38,17 @@ private sealed class UnsupportedConstraintMessageKind {
     private val constraintTraitsUberIssue = "https://github.com/awslabs/smithy-rs/issues/1401"
 
     fun intoLogMessage(ignoreUnsupportedConstraints: Boolean): LogMessage {
-        fun buildMessage(intro: String, willSupport: Boolean, trackingIssue: String, canBeIgnored: Boolean = true): String {
+        fun buildMessage(intro: String, willSupport: Boolean, trackingIssue: String? = null, canBeIgnored: Boolean = true): String {
             var msg = """
-                $intro
+                    $intro
                     This is not supported in the smithy-rs server SDK."""
             if (willSupport) {
                 msg += """
-                    It will be supported in the future. See the tracking issue ($trackingIssue)."""
+                    It will be supported in the future."""
+            }
+            if (trackingIssue != null) {
+                msg += """
+                    For more information, and to report if you're affected by this, please use the tracking issue: $trackingIssue."""
             }
             if (canBeIgnored) {
                 msg += """
@@ -106,6 +112,19 @@ private sealed class UnsupportedConstraintMessageKind {
                 level,
                 buildMessageShapeHasUnsupportedConstraintTrait(shape, uniqueItemsTrait, constraintTraitsUberIssue),
             )
+
+            is UnsupportedMapShapeReachableFromUniqueItemsList -> LogMessage(
+                Level.SEVERE,
+                buildMessage(
+                    """
+                    The map shape `${mapShape.id}` is reachable from the list shape `${listShape.id}`, which has the 
+                    `@uniqueItems` trait attached.
+                    """.trimIndent().replace("\n", " "),
+                    willSupport = false,
+                    trackingIssue = "https://github.com/awslabs/smithy/issues/1567",
+                    canBeIgnored = false,
+                ),
+            )
         }
     }
 }
@@ -129,6 +148,12 @@ private data class UnsupportedRangeTraitOnShape(val shape: Shape, val rangeTrait
 private data class UnsupportedUniqueItemsTraitOnShape(val shape: Shape, val uniqueItemsTrait: UniqueItemsTrait) :
     UnsupportedConstraintMessageKind()
 
+private data class UnsupportedMapShapeReachableFromUniqueItemsList(
+    val listShape: ListShape,
+    val uniqueItemsTrait: UniqueItemsTrait,
+    val mapShape: MapShape,
+) : UnsupportedConstraintMessageKind()
+
 data class LogMessage(val level: Level, val message: String)
 data class ValidationResult(val shouldAbort: Boolean, val messages: List<LogMessage>) :
     Throwable(message = messages.joinToString("\n") { it.message })
@@ -246,11 +271,29 @@ fun validateUnsupportedConstraints(
         .map { (shape, rangeTrait) -> UnsupportedRangeTraitOnShape(shape, rangeTrait as RangeTrait) }
         .toSet()
 
+    // 5. `@uniqueItems` cannot reach a map shape.
+    // See https://github.com/awslabs/smithy/issues/1567.
+    val mapShapeReachableFromUniqueItemsListShapeSet = walker
+        .walkShapes(service)
+        .asSequence()
+        .filterMapShapesToTraits(setOf(UniqueItemsTrait::class.java))
+        .flatMap { (listShape, uniqueItemsTrait) ->
+            walker.walkShapes(listShape).filterIsInstance<MapShape>().map { mapShape ->
+                UnsupportedMapShapeReachableFromUniqueItemsList(
+                    listShape as ListShape,
+                    uniqueItemsTrait as UniqueItemsTrait,
+                    mapShape,
+                )
+            }
+        }
+        .toSet()
+
     val messages =
         unsupportedConstraintOnMemberShapeSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) } +
             unsupportedLengthTraitOnStreamingBlobShapeSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) } +
             unsupportedConstraintShapeReachableViaAnEventStreamSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) } +
-            unsupportedRangeTraitOnShapeSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) }
+            unsupportedRangeTraitOnShapeSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) } +
+            mapShapeReachableFromUniqueItemsListShapeSet.map { it.intoLogMessage(codegenConfig.ignoreUnsupportedConstraints) }
 
     return ValidationResult(shouldAbort = messages.any { it.level == Level.SEVERE }, messages)
 }
diff --git a/codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraintsAreNotUsedTest.kt b/codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraintsAreNotUsedTest.kt
index 7e111f758cf..9a7ba2bf95f 100644
--- a/codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraintsAreNotUsedTest.kt
+++ b/codegen-server/src/test/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ValidateUnsupportedConstraintsAreNotUsedTest.kt
@@ -27,7 +27,6 @@ internal class ValidateUnsupportedConstraintsAreNotUsedTest {
         namespace test
 
         service TestService {
-            version: "123",
             operations: [TestOperation]
         }
 
@@ -186,6 +185,47 @@ internal class ValidateUnsupportedConstraintsAreNotUsedTest {
         }
     }
 
+    private val mapShapeReachableFromUniqueItemsListShapeModel =
+        """
+        $baseModel
+        
+        structure TestInputOutput {
+            uniqueItemsList: UniqueItemsList
+        }
+        
+        @uniqueItems
+        list UniqueItemsList {
+            member: Map
+        }
+        
+        map Map {
+            key: String
+            value: String
+        }
+        """.asSmithyModel()
+
+    @Test
+    fun `it should detect when a map shape is reachable from a uniqueItems list shape`() {
+        val validationResult = validateModel(mapShapeReachableFromUniqueItemsListShapeModel)
+
+        validationResult.messages shouldHaveSize 1
+        validationResult.shouldAbort shouldBe true
+        validationResult.messages[0].message shouldContain """
+            The map shape `test#Map` is reachable from the list shape `test#UniqueItemsList`, which has the 
+            `@uniqueItems` trait attached.
+        """.trimIndent().replace("\n", " ")
+    }
+
+    @Test
+    fun `it should abort when a map shape is reachable from a uniqueItems list shape, despite opting into ignoreUnsupportedConstraintTraits`() {
+        val validationResult = validateModel(
+            mapShapeReachableFromUniqueItemsListShapeModel,
+            ServerCodegenConfig().copy(ignoreUnsupportedConstraints = true),
+        )
+
+        validationResult.shouldAbort shouldBe true
+    }
+
     @Test
     fun `it should abort when constraint traits in event streams are used, despite opting into ignoreUnsupportedConstraintTraits`() {
         val validationResult = validateModel(