diff --git a/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt b/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt
index 5bba552..6ea3494 100644
--- a/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt
+++ b/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt
@@ -58,9 +58,9 @@ public class AdapterGenerator(
 ) {
 
   private companion object {
-    private val INT_TYPE_BLOCK = CodeBlock.of("%T::class.javaPrimitiveType", INT)
+    private val INT_TYPE_BLOCK = CodeBlock.of("%T::class.javaPrimitiveType!!", INT)
     private val DEFAULT_CONSTRUCTOR_MARKER_TYPE_BLOCK = CodeBlock.of(
-      "%M",
+      "%M!!",
       MemberName(MOSHI_UTIL_PACKAGE, "DEFAULT_CONSTRUCTOR_MARKER"),
     )
     private val CN_MOSHI = Moshi::class.asClassName()
diff --git a/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/kotlintypes.kt b/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/kotlintypes.kt
index 6d22ebf..9e84a95 100644
--- a/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/kotlintypes.kt
+++ b/moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/kotlintypes.kt
@@ -118,7 +118,7 @@ internal fun TypeName.asTypeBlock(): CodeBlock {
             // Remove nullable but keep the java object type
             CodeBlock.of("%T::class.javaObjectType", copy(nullable = false))
           } else {
-            CodeBlock.of("%T::class.javaPrimitiveType", this)
+            CodeBlock.of("%T::class.javaPrimitiveType!!", this)
           }
         }
         UNIT, Void::class.asTypeName(), NOTHING -> throw IllegalStateException("Parameter with void, Unit, or Nothing type is illegal")