diff --git a/kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/TypeRenderer.kt b/kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/TypeRenderer.kt
index e1259eb..d6957fc 100644
--- a/kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/TypeRenderer.kt
+++ b/kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/TypeRenderer.kt
@@ -43,6 +43,16 @@ abstract class TypeRenderer {
 
   fun render(typeName: TypeName): CodeBlock {
     if (typeName.nullable) {
+      if (typeName == BOOLEAN.asNullable()
+          || typeName == BYTE.asNullable()
+          || typeName == CHAR.asNullable()
+          || typeName == DOUBLE.asNullable()
+          || typeName == FLOAT.asNullable()
+          || typeName == INT.asNullable()
+          || typeName == LONG.asNullable()
+          || typeName == SHORT.asNullable()) {
+        return CodeBlock.of("%T::class.javaObjectType", typeName.asNonNullable())
+      }
       return render(typeName.asNonNullable())
     }
 
diff --git a/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/codgen/GeneratedAdaptersTest.kt b/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/codgen/GeneratedAdaptersTest.kt
index 1305d41..c5eca06 100644
--- a/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/codgen/GeneratedAdaptersTest.kt
+++ b/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/codgen/GeneratedAdaptersTest.kt
@@ -17,9 +17,12 @@ package com.squareup.moshi.kotlin.codgen
 
 import com.squareup.moshi.FromJson
 import com.squareup.moshi.Json
+import com.squareup.moshi.JsonAdapter
 import com.squareup.moshi.JsonClass
 import com.squareup.moshi.JsonDataException
 import com.squareup.moshi.JsonQualifier
+import com.squareup.moshi.JsonReader
+import com.squareup.moshi.JsonWriter
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.ToJson
 import com.squareup.moshi.Types
@@ -28,6 +31,7 @@ import org.intellij.lang.annotations.Language
 import org.junit.Assert.fail
 import org.junit.Ignore
 import org.junit.Test
+import java.lang.reflect.Type
 import java.util.Locale
 
 class GeneratedAdaptersTest {
@@ -865,6 +869,36 @@ class GeneratedAdaptersTest {
       return s.toLowerCase(Locale.US)
     }
   }
+
+  @JsonClass(generateAdapter = true)
+  data class HasNullableBoolean(val boolean: Boolean?)
+
+  @Test fun nullablePrimitivesUseBoxedPrimitiveAdapters() {
+    val moshi = Moshi.Builder()
+        .add(JsonAdapter.Factory { type, annotations, moshi ->
+          if (Boolean::class.javaObjectType == type) {
+            return@Factory object:JsonAdapter<Boolean?>() {
+              override fun fromJson(reader: JsonReader): Boolean? {
+                if (reader.peek() != JsonReader.Token.BOOLEAN) {
+                  reader.skipValue()
+                  return null
+                }
+                return reader.nextBoolean()
+              }
+
+              override fun toJson(writer: JsonWriter, value: Boolean?) {
+                writer.value(value)
+              }
+            }
+          }
+          null
+        })
+        .build()
+    val adapter = moshi.adapter(HasNullableBoolean::class.java).serializeNulls()
+    assertThat(adapter.fromJson("""{"boolean":"not a boolean"}"""))
+        .isEqualTo(HasNullableBoolean(null))
+    assertThat(adapter.toJson(HasNullableBoolean(null))).isEqualTo("""{"boolean":null}""")
+  }
 }
 
 // Has to be outside to avoid Types seeing an owning class
diff --git a/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/reflect/KotlinJsonAdapterTest.kt b/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/reflect/KotlinJsonAdapterTest.kt
index 87499f6..d1a7df3 100644
--- a/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/reflect/KotlinJsonAdapterTest.kt
+++ b/kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/reflect/KotlinJsonAdapterTest.kt
@@ -17,9 +17,12 @@ package com.squareup.moshi.kotlin.reflect
 
 import com.squareup.moshi.FromJson
 import com.squareup.moshi.Json
+import com.squareup.moshi.JsonAdapter
 import com.squareup.moshi.JsonClass
 import com.squareup.moshi.JsonDataException
 import com.squareup.moshi.JsonQualifier
+import com.squareup.moshi.JsonReader
+import com.squareup.moshi.JsonWriter
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.ToJson
 import com.squareup.moshi.Types
@@ -881,4 +884,33 @@ class KotlinJsonAdapterTest {
       return s.toLowerCase(Locale.US)
     }
   }
+
+  data class HasNullableBoolean(val boolean: Boolean?)
+
+  @Test fun nullablePrimitivesUseBoxedPrimitiveAdapters() {
+    val moshi = Moshi.Builder()
+        .add(JsonAdapter.Factory { type, annotations, moshi ->
+          if (Boolean::class.javaObjectType == type) {
+            return@Factory object: JsonAdapter<Boolean?>() {
+              override fun fromJson(reader: JsonReader): Boolean? {
+                if (reader.peek() != JsonReader.Token.BOOLEAN) {
+                  reader.skipValue()
+                  return null
+                }
+                return reader.nextBoolean()
+              }
+
+              override fun toJson(writer: JsonWriter, value: Boolean?) {
+                writer.value(value)
+              }
+            }
+          }
+          null
+        })
+        .build()
+    val adapter = moshi.adapter(HasNullableBoolean::class.java).serializeNulls()
+    assertThat(adapter.fromJson("""{"boolean":"not a boolean"}"""))
+        .isEqualTo(HasNullableBoolean(null))
+    assertThat(adapter.toJson(HasNullableBoolean(null))).isEqualTo("""{"boolean":null}""")
+  }
 }