diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index a99b8c59a8..cdb838524a 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -28,3 +28,9 @@ message = "The `AssumeRoleBuilder::policy_arns` now accepts strings instead of a
 references = ["smithy-rs#3205"]
 meta = { "breaking" = true, "tada" = false, "bug" = false }
 author = "rcoh"
+
+[[aws-sdk-rust]]
+message = "Make certain types for EMR Serverless optional. Previously, they defaulted to 0, but this created invalid requests."
+references = ["smithy-rs#3217"]
+meta = { "breaking" = true, "tada" = false, "bug" = true }
+author = "milesziemer"
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt
index 59ef326a2f..5e694c1cea 100644
--- a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt
@@ -10,6 +10,7 @@ import software.amazon.smithy.rust.codegen.client.smithy.customizations.DocsRsMe
 import software.amazon.smithy.rust.codegen.client.smithy.customize.ClientCodegenDecorator
 import software.amazon.smithy.rust.codegen.client.smithy.customize.CombinedClientCodegenDecorator
 import software.amazon.smithy.rustsdk.customize.DisabledAuthDecorator
+import software.amazon.smithy.rustsdk.customize.RemoveDefaultsDecorator
 import software.amazon.smithy.rustsdk.customize.apigateway.ApiGatewayDecorator
 import software.amazon.smithy.rustsdk.customize.applyDecorators
 import software.amazon.smithy.rustsdk.customize.ec2.Ec2Decorator
@@ -53,6 +54,7 @@ val DECORATORS: List<ClientCodegenDecorator> = listOf(
         RecursionDetectionDecorator(),
         InvocationIdDecorator(),
         RetryInformationHeaderDecorator(),
+        RemoveDefaultsDecorator(),
     ),
 
     // Service specific decorators
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaults.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaults.kt
new file mode 100644
index 0000000000..bebfd639b2
--- /dev/null
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaults.kt
@@ -0,0 +1,58 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rustsdk.customize
+
+import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.shapes.AbstractShapeBuilder
+import software.amazon.smithy.model.shapes.MemberShape
+import software.amazon.smithy.model.shapes.Shape
+import software.amazon.smithy.model.shapes.ShapeId
+import software.amazon.smithy.model.traits.DefaultTrait
+import software.amazon.smithy.model.transform.ModelTransformer
+import software.amazon.smithy.rust.codegen.core.util.hasTrait
+import software.amazon.smithy.rust.codegen.core.util.letIf
+import software.amazon.smithy.utils.ToSmithyBuilder
+import java.util.logging.Logger
+
+/**
+ * Removes default values from specified root shapes, and any members that target those
+ * root shapes.
+ */
+object RemoveDefaults {
+    private val logger: Logger = Logger.getLogger(javaClass.name)
+
+    fun processModel(model: Model, removeDefaultsFrom: Set<ShapeId>): Model {
+        val removedRootDefaults: MutableSet<ShapeId> = HashSet()
+        val removedRootDefaultsModel = ModelTransformer.create().mapShapes(model) { shape ->
+            shape.letIf(shouldRemoveRootDefault(shape, removeDefaultsFrom)) {
+                logger.info("Removing default trait from root $shape")
+                removedRootDefaults.add(shape.id)
+                removeDefault(shape)
+            }
+        }
+
+        return ModelTransformer.create().mapShapes(removedRootDefaultsModel) { shape ->
+            shape.letIf(shouldRemoveMemberDefault(shape, removedRootDefaults)) {
+                logger.info("Removing default trait from member $shape")
+                removeDefault(shape)
+            }
+        }
+    }
+
+    private fun shouldRemoveRootDefault(shape: Shape, removeDefaultsFrom: Set<ShapeId>): Boolean {
+        return shape !is MemberShape && removeDefaultsFrom.contains(shape.id) && shape.hasTrait<DefaultTrait>()
+    }
+
+    private fun shouldRemoveMemberDefault(shape: Shape, removeDefaultsFrom: Set<ShapeId>): Boolean {
+        return shape is MemberShape && removeDefaultsFrom.contains(shape.target) && shape.hasTrait<DefaultTrait>()
+    }
+
+    private fun removeDefault(shape: Shape): Shape {
+        return ((shape as ToSmithyBuilder<*>).toBuilder() as AbstractShapeBuilder<*, *>)
+            .removeTrait(DefaultTrait.ID)
+            .build()
+    }
+}
diff --git a/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsDecorator.kt b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsDecorator.kt
new file mode 100644
index 0000000000..91623f3d96
--- /dev/null
+++ b/aws/sdk-codegen/src/main/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsDecorator.kt
@@ -0,0 +1,43 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rustsdk.customize
+
+import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.shapes.ServiceShape
+import software.amazon.smithy.rust.codegen.client.smithy.ClientRustSettings
+import software.amazon.smithy.rust.codegen.client.smithy.customize.ClientCodegenDecorator
+import software.amazon.smithy.rust.codegen.core.util.shapeId
+import java.util.logging.Logger
+
+/**
+ * Removes default values from certain shapes, and any member that targets those shapes,
+ * for some services where the default value causes serialization issues, validation
+ * issues, or other unexpected behavior.
+ */
+class RemoveDefaultsDecorator : ClientCodegenDecorator {
+    override val name: String = "RemoveDefaults"
+    override val order: Byte = 0
+    private val logger: Logger = Logger.getLogger(javaClass.name)
+
+    // Service shape id -> Shape id of each root shape to remove the default from.
+    private val removeDefaults = mapOf(
+        "com.amazonaws.emrserverless#AwsToledoWebService".shapeId() to setOf(
+            // Service expects this to have a min value > 0
+            "com.amazonaws.emrserverless#WorkerCounts".shapeId(),
+        ),
+    )
+
+    private fun applies(service: ServiceShape) =
+        removeDefaults.containsKey(service.id)
+
+    override fun transformModel(service: ServiceShape, model: Model, settings: ClientRustSettings): Model {
+        if (!applies(service)) {
+            return model
+        }
+        logger.info("Removing invalid defaults from ${service.id}")
+        return RemoveDefaults.processModel(model, removeDefaults[service.id]!!)
+    }
+}
diff --git a/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsTest.kt b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsTest.kt
new file mode 100644
index 0000000000..266c3d6be3
--- /dev/null
+++ b/aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/customize/RemoveDefaultsTest.kt
@@ -0,0 +1,41 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rustsdk.customize
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import software.amazon.smithy.model.shapes.IntegerShape
+import software.amazon.smithy.model.shapes.MemberShape
+import software.amazon.smithy.model.traits.DefaultTrait
+import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
+import software.amazon.smithy.rust.codegen.core.util.hasTrait
+import software.amazon.smithy.rust.codegen.core.util.lookup
+import software.amazon.smithy.rust.codegen.core.util.shapeId
+
+internal class RemoveDefaultsTest {
+    @Test
+    fun `defaults should be removed`() {
+        val removeDefaults = setOf(
+            "test#Bar".shapeId(),
+        )
+        val baseModel = """
+            namespace test
+
+            structure Foo {
+                bar: Bar = 0
+            }
+
+            @default(0)
+            integer Bar
+
+        """.asSmithyModel(smithyVersion = "2.0")
+        val model = RemoveDefaults.processModel(baseModel, removeDefaults)
+        val member = model.lookup<MemberShape>("test#Foo\$bar")
+        member.hasTrait<DefaultTrait>() shouldBe false
+        val root = model.lookup<IntegerShape>("test#Bar")
+        root.hasTrait<DefaultTrait>() shouldBe false
+    }
+}