diff --git a/compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/PackagePartClassUtils.java b/compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/PackagePartClassUtils.java
index afc9f481487..6c027bcf2b3 100644
--- a/compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/PackagePartClassUtils.java
+++ b/compiler/frontend.java/src/org/jetbrains/kotlin/load/kotlin/PackagePartClassUtils.java
@@ -41,10 +41,7 @@ import static org.jetbrains.kotlin.load.kotlin.PackageClassUtils.getPackageClass
 
 public class PackagePartClassUtils {
     public static int getPathHashCode(@NotNull VirtualFile file) {
-        // Conversion to system-dependent name seems to be unnecessary, but it's hard to check now:
-        // it was introduced when fixing KT-2839, which appeared again (KT-3639).
-        // If you try to remove it, run tests on Windows.
-        return FileUtil.toSystemDependentName(file.getPath()).hashCode();
+        return file.getPath().toLowerCase().hashCode();
     }
 
     @NotNull
diff --git a/jps-plugin/test/org/jetbrains/kotlin/jps/build/IncrementalProjectPathCaseChangedTest.kt b/jps-plugin/test/org/jetbrains/kotlin/jps/build/IncrementalProjectPathCaseChangedTest.kt
index 9a7d734a87e..27cb4449ec7 100644
--- a/jps-plugin/test/org/jetbrains/kotlin/jps/build/IncrementalProjectPathCaseChangedTest.kt
+++ b/jps-plugin/test/org/jetbrains/kotlin/jps/build/IncrementalProjectPathCaseChangedTest.kt
@@ -24,6 +24,10 @@ public class IncrementalProjectPathCaseChangedTest : AbstractIncrementalJpsTest(
         doTest("jps-plugin/testData/incremental/custom/projectPathCaseChanged/")
     }
 
+    fun testProjectPathCaseChangedMultiFile() {
+        doTest("jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/")
+    }
+
     override fun doTest(testDataPath: String) {
         if (SystemInfoRt.isFileSystemCaseSensitive) {
             return
diff --git a/jps-plugin/test/org/jetbrains/kotlin/jps/build/KotlinJpsBuildTest.java b/jps-plugin/test/org/jetbrains/kotlin/jps/build/KotlinJpsBuildTest.java
index c2a386cc95f..b2e15a5f3bc 100644
--- a/jps-plugin/test/org/jetbrains/kotlin/jps/build/KotlinJpsBuildTest.java
+++ b/jps-plugin/test/org/jetbrains/kotlin/jps/build/KotlinJpsBuildTest.java
@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.jps.build;
 import com.google.common.collect.Lists;
 import com.intellij.openapi.util.Condition;
 import com.intellij.openapi.util.io.FileUtil;
+import com.intellij.openapi.util.io.FileUtilRt;
 import com.intellij.testFramework.LightVirtualFile;
 import com.intellij.util.ArrayUtil;
 import com.intellij.util.containers.ContainerUtil;
@@ -614,8 +615,8 @@ public class KotlinJpsBuildTest extends AbstractKotlinJpsBuildTestCase {
     }
 
     private String packagePartClass(String moduleName, String fileName, String packageClassFqName) {
-        File file = new File(workDir, fileName);
-        LightVirtualFile fakeVirtualFile = new LightVirtualFile(file.getPath()) {
+        String path = FileUtilRt.toSystemIndependentName(new File(workDir, fileName).getAbsolutePath());
+        LightVirtualFile fakeVirtualFile = new LightVirtualFile(path) {
             @NotNull
             @Override
             public String getPath() {
diff --git a/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/bar.kt b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/bar.kt
new file mode 100644
index 00000000000..fe45df99555
--- /dev/null
+++ b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/bar.kt
@@ -0,0 +1,2 @@
+fun bar() {
+}
\ No newline at end of file
diff --git a/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/build.log b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/build.log
new file mode 100644
index 00000000000..4cf233bbc00
--- /dev/null
+++ b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/build.log
@@ -0,0 +1,7 @@
+Cleaning output files:
+out/production/module/_DefaultPackage$foo$*.class
+out/production/module/_DefaultPackage.class
+End of files
+Compiling files:
+src/foo.kt
+End of files
\ No newline at end of file
diff --git a/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt
new file mode 100644
index 00000000000..f23d7f69d2f
--- /dev/null
+++ b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt
@@ -0,0 +1,2 @@
+fun foo() {
+}
\ No newline at end of file
diff --git a/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt.new b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt.new
new file mode 100644
index 00000000000..f23d7f69d2f
--- /dev/null
+++ b/jps-plugin/testData/incremental/custom/projectPathCaseChangedMultiFile/foo.kt.new
@@ -0,0 +1,2 @@
+fun foo() {
+}
\ No newline at end of file