diff --git a/gradle/docs.gradle b/gradle/docs.gradle
index be68b7f0ff..510144e575 100644
--- a/gradle/docs.gradle
+++ b/gradle/docs.gradle
@@ -66,7 +66,8 @@ dokka {
 	outputDirectory = "$buildDir/docs/kdoc"
 
 	sourceDirs = files(subprojects.collect { project ->
-		project.sourceSets.main.kotlin.srcDirs
+		def kotlinDirs = project.sourceSets.main.kotlin.srcDirs.collect()
+		kotlinDirs -= project.sourceSets.main.java.srcDirs
 	})
 	externalDocumentationLink {
 		url = new URL("http://docs.spring.io/spring-framework/docs/${version}/javadoc-api/")