diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 64d434f5f9cc1d5fc6db67fa380a4d4de47ca2d0..edfc6e29c6a8a406f2a78efe9c42ca31e728b193 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -9,6 +9,6 @@ repos:
   rev: v1.6.1
   hooks:
   - id: pretty-format-kotlin
-    args: [--autofix, --ktlint-version, 0.39.0]
+    args: [--autofix, --ktlint-version, 0.40.0]
   - id: pretty-format-yaml
     args: [--autofix, --indent, '2']
diff --git a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/lang/RustWriter.kt b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/lang/RustWriter.kt
index 1b870ec8771b3e9effbeededde30f4747edee4d4..f8bb003464c27c19ede50e9eaa7035e6e4950794 100644
--- a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/lang/RustWriter.kt
+++ b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/lang/RustWriter.kt
@@ -29,7 +29,7 @@ fun <T : CodeWriter> T.withBlock(
     vararg args: Any,
     block: T.() -> Unit
 ): T {
-    return conditionalBlock(textBeforeNewLine, textAfterNewLine, conditional = true, block = block, args = *args)
+    return conditionalBlock(textBeforeNewLine, textAfterNewLine, conditional = true, block = block, args = args)
 }
 
 /**
diff --git a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
index 98df6822268be486545b150783346a9a7b36f478..a9f42bf09015bcdb0cbbb02e19a81622516731cd 100644
--- a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
+++ b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/SymbolVisitor.kt
@@ -42,10 +42,11 @@ import software.amazon.smithy.rust.codegen.smithy.traits.SyntheticInputTrait
 import software.amazon.smithy.rust.codegen.smithy.traits.SyntheticOutputTrait
 import software.amazon.smithy.rust.codegen.util.toSnakeCase
 import software.amazon.smithy.utils.StringUtils
+import kotlin.reflect.KClass
 
 // TODO: currently, respecting integer types.
 // Should we not? [Go does not]
-val SimpleShapes = mapOf(
+val SimpleShapes: Map<KClass<out Shape>, RustType> = mapOf(
     BooleanShape::class to RustType.Bool,
     FloatShape::class to RustType.Float(32),
     DoubleShape::class to RustType.Float(64),
diff --git a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxer.kt b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxer.kt
index 361f301fff722c711bca5cbe9a93b237cc6b390a..b9a3563f0b7d7e81fe3f76c3f49a79eb1338a61c 100644
--- a/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxer.kt
+++ b/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/smithy/transformers/RecursiveShapeBoxer.kt
@@ -59,7 +59,7 @@ object RecursiveShapeBoxer {
         return loopToFix?.let { loop: List<Shape> ->
             check(loop.isNotEmpty())
             // pick the shape to box in a deterministic way
-            val shapeToBox = loop.filterIsInstance<MemberShape>().minBy { it.id }!!
+            val shapeToBox = loop.filterIsInstance<MemberShape>().minByOrNull { it.id }!!
             ModelTransformer.create().mapShapes(model) { shape ->
                 if (shape == shapeToBox) {
                     shape.asMemberShape().get().toBuilder().addTrait(RustBoxTrait()).build()
diff --git a/codegen/src/test/kotlin/software/amazon/smithy/rust/testutil/Rust.kt b/codegen/src/test/kotlin/software/amazon/smithy/rust/testutil/Rust.kt
index 3eb0fa9c1b9e473d9c69fbc670dfeb2db75508b1..af10ac84b76ebfaf7080df0f7ff7260acefd04b2 100644
--- a/codegen/src/test/kotlin/software/amazon/smithy/rust/testutil/Rust.kt
+++ b/codegen/src/test/kotlin/software/amazon/smithy/rust/testutil/Rust.kt
@@ -27,15 +27,28 @@ import software.amazon.smithy.rust.codegen.util.CommandFailed
 import software.amazon.smithy.rust.codegen.util.dq
 import software.amazon.smithy.rust.codegen.util.runCommand
 import java.io.File
+import java.nio.file.Files.createTempDirectory
 import java.nio.file.Path
 
+/**
+ * Waiting for Kotlin to stabilize their temp directory stuff
+ */
+private fun tempDir(directory: File? = null): File {
+    return if (directory != null) {
+        createTempDirectory(directory.toPath(), "smithy-test").toFile()
+    } else {
+        createTempDirectory("smithy-test").toFile()
+    }
+}
+
 /**
  * Creates a Cargo workspace shared among all tests
  *
  * This workspace significantly improves test performance by sharing dependencies between different tests.
  */
 object TestWorkspace {
-    private val baseDir = System.getenv("SMITHY_TEST_WORKSPACE")?.let { File(it) } ?: createTempDir()
+    private val baseDir =
+        System.getenv("SMITHY_TEST_WORKSPACE")?.let { File(it) } ?: tempDir()
     private val subprojects = mutableListOf<String>()
 
     init {
@@ -56,7 +69,7 @@ object TestWorkspace {
 
     fun subproject(): File {
         synchronized(subprojects) {
-            val newProject = createTempDir(directory = baseDir)
+            val newProject = tempDir(directory = baseDir)
             subprojects.add(newProject.name)
             generate()
             return newProject
@@ -114,7 +127,7 @@ fun TestWriterDelegator.compileAndTest() {
 // TODO: unify these test helpers a bit
 fun String.shouldParseAsRust() {
     // quick hack via rustfmt
-    val tempFile = createTempFile(suffix = ".rs")
+    val tempFile = File.createTempFile("rust_test", ".rs")
     tempFile.writeText(this)
     "rustfmt ${tempFile.absolutePath}".runCommand()
 }
@@ -205,8 +218,8 @@ fun String.compileAndTest(
 
 fun String.shouldCompile(): File {
     this.shouldParseAsRust()
-    val tempFile = createTempFile(suffix = ".rs")
-    val tempDir = createTempDir()
+    val tempFile = File.createTempFile("rust_test", ".rs")
+    val tempDir = tempDir()
     tempFile.writeText(this)
     if (!this.contains("fn main")) {
         tempFile.appendText("\nfn main() {}\n")
diff --git a/gradle.properties b/gradle.properties
index 71822fe198e3b2741d5d778be049080f3874a53a..b3b3b69ea9bd36a5bd262f6aa737d492bb98e3e2 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -6,10 +6,10 @@
 kotlin.code.style=official
 
 # codegen
-smithyVersion=1.4.0
+smithyVersion=1.5.0
 
 # kotlin
-kotlinVersion=1.3.72
+kotlinVersion=1.4.21
 kotlin.native.ignoreDisabledTargets=true
 
 # kotlin libraries
@@ -20,5 +20,5 @@ ktorVersion=1.3.2
 # testing/utility
 # FIXME - junit5 not working
 junitVersion=4.12
-ktlintVersion=0.39.0
+ktlintVersion=0.40.0
 kotestVersion=4.2.6