diff --git a/internal/zinc-core/src/main/scala/sbt/internal/inc/Analysis.scala b/internal/zinc-core/src/main/scala/sbt/internal/inc/Analysis.scala
index 7be46d9f33..4218d3297c 100644
--- a/internal/zinc-core/src/main/scala/sbt/internal/inc/Analysis.scala
+++ b/internal/zinc-core/src/main/scala/sbt/internal/inc/Analysis.scala
@@ -98,13 +98,20 @@ object Analysis {
 
   def empty: Analysis = Empty
 
-  def summary(a: Analysis): String = {
+  case class Sources(java: Set[String], scala: Set[String])
+
+  def sources(a: Analysis): Sources = {
     def sourceFileForClass(className: String): VirtualFileRef =
       a.relations.definesClass(className).headOption.getOrElse {
         sys.error(s"Can't find source file for $className")
       }
     def isJavaClass(className: String) = sourceFileForClass(className).id.endsWith(".java")
     val (j, s) = a.apis.allInternalClasses.partition(isJavaClass)
+    Sources(j.toSet, s.toSet)
+  }
+
+  def summary(a: Analysis): String = {
+    val Sources(j, s) = sources(a)
     val c = a.stamps.allProducts
     val ext = a.apis.allExternals
     val jars = a.relations.allLibraryDeps.filter(_.id.endsWith(".jar"))
diff --git a/internal/zinc-core/src/main/scala/sbt/internal/inc/IncrementalCommon.scala b/internal/zinc-core/src/main/scala/sbt/internal/inc/IncrementalCommon.scala
index dd14826794..9803ccdd6a 100644
--- a/internal/zinc-core/src/main/scala/sbt/internal/inc/IncrementalCommon.scala
+++ b/internal/zinc-core/src/main/scala/sbt/internal/inc/IncrementalCommon.scala
@@ -188,8 +188,10 @@ private[inc] abstract class IncrementalCommon(
         val continue = nextInvalidations.nonEmpty &&
           lookup.shouldDoIncrementalCompilation(nextInvalidations, analysis)
 
-        // If we're completing the cycle, then mergeAndInvalidate has already been called
-        if (!completingCycle) {
+        val hasScala = Analysis.sources(partialAnalysis).scala.nonEmpty
+
+        // If we're completing the cycle and we had scala sources, then mergeAndInvalidate has already been called
+        if (!completingCycle || !hasScala) {
           registerCycle(recompiledClasses, newApiChanges, nextInvalidations, continue)
         }
         CompileCycleResult(continue, nextInvalidations, analysis)