diff --git a/build.gradle.kts b/build.gradle.kts
index eef5c732..4497a9ea 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -131,13 +131,13 @@ subprojects {
     }
 
     dependencies {
-        implementation(kotlin("stdlib-jdk8"))
+        api(kotlin("stdlib-jdk8"))
+        api("org.jetbrains.kotlinx:kotlinx-coroutines-core")
         implementation(kotlin("reflect"))
-        implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core")
         implementation("org.reflections:reflections")
         implementation("org.apache.commons:commons-text")
         arrayOf("core", "annotations", "databind").forEach { name ->
-            implementation(jacksonCore(name))
+            api(jacksonCore(name))
         }
         implementation(jackson("module", "kotlin"))
         implementation(jackson("datatype", "jsr310"))
diff --git a/konf-all/build.gradle.kts b/konf-all/build.gradle.kts
index 87a903b4..e1a3387a 100644
--- a/konf-all/build.gradle.kts
+++ b/konf-all/build.gradle.kts
@@ -26,7 +26,7 @@ dependencies {
         ":konf-xml",
         ":konf-yaml"
     )) {
-        implementation(project(name))
+        api(project(name))
         testImplementation(project(name).dependencyProject.sourceSets["test"].output)
     }
 
diff --git a/konf-git/build.gradle.kts b/konf-git/build.gradle.kts
index 78874f65..15358011 100644
--- a/konf-git/build.gradle.kts
+++ b/konf-git/build.gradle.kts
@@ -5,8 +5,8 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
-    implementation("org.eclipse.jgit:org.eclipse.jgit")
+    api(project(":konf-core"))
+    api("org.eclipse.jgit:org.eclipse.jgit")
 
     val test by project(":konf-core").dependencyProject.sourceSets
     testImplementation(test.output)
diff --git a/konf-hocon/build.gradle.kts b/konf-hocon/build.gradle.kts
index 1241f6c6..e75700cf 100644
--- a/konf-hocon/build.gradle.kts
+++ b/konf-hocon/build.gradle.kts
@@ -5,7 +5,7 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
+    api(project(":konf-core"))
     implementation("com.typesafe:config")
 
     val test by project(":konf-core").dependencyProject.sourceSets
diff --git a/konf-hocon/src/main/kotlin/com/uchuhimo/konf/source/hocon/HoconSource.kt b/konf-hocon/src/main/kotlin/com/uchuhimo/konf/source/hocon/HoconSource.kt
index eb990a1c..18ccac64 100644
--- a/konf-hocon/src/main/kotlin/com/uchuhimo/konf/source/hocon/HoconSource.kt
+++ b/konf-hocon/src/main/kotlin/com/uchuhimo/konf/source/hocon/HoconSource.kt
@@ -28,7 +28,7 @@ import com.uchuhimo.konf.source.Source
 import com.uchuhimo.konf.source.SourceInfo
 import com.uchuhimo.konf.source.ValueSourceNode
 
-fun ConfigValue.toTree(): TreeNode {
+private fun ConfigValue.toTree(): TreeNode {
     return when (valueType()!!) {
         ConfigValueType.NULL -> NullSourceNode
         ConfigValueType.BOOLEAN, ConfigValueType.NUMBER, ConfigValueType.STRING -> ValueSourceNode(unwrapped())
@@ -48,7 +48,7 @@ fun ConfigValue.toTree(): TreeNode {
 /**
  * Source from a HOCON value.
  */
-class HoconSource(
+internal class HoconSource(
     val value: ConfigValue
 ) : Source {
     override val info: SourceInfo = SourceInfo("type" to "HOCON")
diff --git a/konf-hocon/src/test/kotlin/com/uchuhimo/konf/source/hocon/HoconSourceSpec.kt b/konf-hocon/src/test/kotlin/com/uchuhimo/konf/source/hocon/HoconSourceSpec.kt
index 35a0f3f1..d9cfddfd 100644
--- a/konf-hocon/src/test/kotlin/com/uchuhimo/konf/source/hocon/HoconSourceSpec.kt
+++ b/konf-hocon/src/test/kotlin/com/uchuhimo/konf/source/hocon/HoconSourceSpec.kt
@@ -29,7 +29,7 @@ import org.jetbrains.spek.api.dsl.it
 import org.jetbrains.spek.api.dsl.on
 import org.jetbrains.spek.subject.SubjectSpek
 
-object HoconSourceSpec : SubjectSpek<HoconSource>({
+internal object HoconSourceSpec : SubjectSpek<HoconSource>({
     subject { HoconProvider.string("key = 1") as HoconSource }
 
     given("a HOCON source") {
diff --git a/konf-js/build.gradle.kts b/konf-js/build.gradle.kts
index 3609c37a..a08b52b9 100644
--- a/konf-js/build.gradle.kts
+++ b/konf-js/build.gradle.kts
@@ -6,7 +6,7 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
+    api(project(":konf-core"))
     implementation("org.graalvm.sdk:graal-sdk")
     implementation("org.graalvm.js:js")
 
diff --git a/konf-toml/build.gradle.kts b/konf-toml/build.gradle.kts
index 3568b4c0..ee706bca 100644
--- a/konf-toml/build.gradle.kts
+++ b/konf-toml/build.gradle.kts
@@ -5,7 +5,7 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
+    api(project(":konf-core"))
     implementation("com.moandjiezana.toml:toml4j")
 
     val test by project(":konf-core").dependencyProject.sourceSets
diff --git a/konf-xml/build.gradle.kts b/konf-xml/build.gradle.kts
index 16f62214..15a073cd 100644
--- a/konf-xml/build.gradle.kts
+++ b/konf-xml/build.gradle.kts
@@ -6,7 +6,7 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
+    api(project(":konf-core"))
     implementation("org.dom4j:dom4j")
     implementation("jaxen:jaxen")
 
diff --git a/konf-yaml/build.gradle.kts b/konf-yaml/build.gradle.kts
index 5e9008bd..05092f30 100644
--- a/konf-yaml/build.gradle.kts
+++ b/konf-yaml/build.gradle.kts
@@ -5,7 +5,7 @@ dependencyManagement {
 }
 
 dependencies {
-    implementation(project(":konf-core"))
+    api(project(":konf-core"))
     implementation("org.yaml:snakeyaml")
 
     val test by project(":konf-core").dependencyProject.sourceSets
diff --git a/konf-yaml/src/main/kotlin/com/uchuhimo/konf/source/yaml/YamlProvider.kt b/konf-yaml/src/main/kotlin/com/uchuhimo/konf/source/yaml/YamlProvider.kt
index a29e891d..bfc58256 100644
--- a/konf-yaml/src/main/kotlin/com/uchuhimo/konf/source/yaml/YamlProvider.kt
+++ b/konf-yaml/src/main/kotlin/com/uchuhimo/konf/source/yaml/YamlProvider.kt
@@ -50,7 +50,7 @@ object YamlProvider : Provider {
     fun get() = this
 }
 
-class YamlConstructor : SafeConstructor() {
+private class YamlConstructor : SafeConstructor() {
     init {
         yamlConstructors[Tag.NULL] = object : AbstractConstruct() {
             override fun construct(node: Node): Any? {