diff --git a/jadx-core/build.gradle b/jadx-core/build.gradle
index a5f47fde1..fa292422d 100644
--- a/jadx-core/build.gradle
+++ b/jadx-core/build.gradle
@@ -4,7 +4,7 @@ dependencies {
     runtime files(jadxClasspath)
 
     compile files('lib/dx-1.13.jar')
-    compile 'commons-io:commons-io:2.4'
+    compile 'commons-io:commons-io:2.6'
     compile 'org.ow2.asm:asm:5.0.3'
     compile 'com.intellij:annotations:12.0'
     compile 'uk.com.robust-it:cloning:1.9.2'
diff --git a/jadx-core/src/main/java/jadx/core/dex/visitors/RenameVisitor.java b/jadx-core/src/main/java/jadx/core/dex/visitors/RenameVisitor.java
index 37a8e4c74..df06281f8 100644
--- a/jadx-core/src/main/java/jadx/core/dex/visitors/RenameVisitor.java
+++ b/jadx-core/src/main/java/jadx/core/dex/visitors/RenameVisitor.java
@@ -1,5 +1,12 @@
 package jadx.core.dex.visitors;
 
+import java.io.File;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.apache.commons.io.FilenameUtils;
+
 import jadx.api.IJadxArgs;
 import jadx.core.Consts;
 import jadx.core.codegen.TypeGen;
@@ -15,20 +22,11 @@ import jadx.core.dex.nodes.FieldNode;
 import jadx.core.dex.nodes.MethodNode;
 import jadx.core.dex.nodes.RootNode;
 import jadx.core.utils.exceptions.JadxException;
+import jadx.core.utils.files.FileUtils;
 import jadx.core.utils.files.InputFile;
 
-import java.io.File;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-
-import org.apache.commons.io.FilenameUtils;
-import org.apache.commons.io.IOCase;
-
 public class RenameVisitor extends AbstractVisitor {
 
-	private static final boolean CASE_SENSITIVE_FS = IOCase.SYSTEM.isCaseSensitive();
-
 	private Deobfuscator deobfuscator;
 
 	@Override
@@ -36,7 +34,7 @@ public class RenameVisitor extends AbstractVisitor {
 		IJadxArgs args = root.getArgs();
 
 		List<DexNode> dexNodes = root.getDexNodes();
-		if (dexNodes.size() == 0) {
+		if (dexNodes.isEmpty()) {
 			return;
 		}
 		InputFile firstInputFile = dexNodes.get(0).getDexFile().getInputFile();
@@ -50,7 +48,8 @@ public class RenameVisitor extends AbstractVisitor {
 		if (deobfuscationOn) {
 			deobfuscator.execute();
 		}
-		checkClasses(root);
+		boolean isCaseSensitive = FileUtils.isCaseSensitiveFS(new File(inputPath)); // args.getOutDir() - not set in gui
+		checkClasses(root, isCaseSensitive);
 	}
 
 	@Override
@@ -63,11 +62,11 @@ public class RenameVisitor extends AbstractVisitor {
 		return false;
 	}
 
-	private void checkClasses(RootNode root) {
+	private void checkClasses(RootNode root, boolean caseSensitive) {
 		Set<String> clsNames = new HashSet<>();
 		for (ClassNode cls : root.getClasses(true)) {
 			checkClassName(cls);
-			if (!CASE_SENSITIVE_FS) {
+			if (!caseSensitive) {
 				ClassInfo classInfo = cls.getClassInfo();
 				String clsFileName = classInfo.getAlias().getFullPath();
 				if (!clsNames.add(clsFileName.toLowerCase())) {
diff --git a/jadx-core/src/main/java/jadx/core/export/ExportGradleProject.java b/jadx-core/src/main/java/jadx/core/export/ExportGradleProject.java
index d6e91f742..e951b0ed5 100644
--- a/jadx-core/src/main/java/jadx/core/export/ExportGradleProject.java
+++ b/jadx-core/src/main/java/jadx/core/export/ExportGradleProject.java
@@ -40,8 +40,8 @@ public class ExportGradleProject {
 
 	public void init() {
 		try {
-			FileUtils.makeDirsForFile(srcOutDir);
-			FileUtils.makeDirsForFile(resOutDir);
+			FileUtils.makeDirs(srcOutDir);
+			FileUtils.makeDirs(resOutDir);
 			saveBuildGradle();
 			skipGeneratedClasses();
 		} catch (Exception e) {
diff --git a/jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java b/jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java
index b7dc28a16..71eae79e7 100644
--- a/jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java
+++ b/jadx-core/src/main/java/jadx/core/utils/files/FileUtils.java
@@ -1,7 +1,5 @@
 package jadx.core.utils.files;
 
-import jadx.core.utils.exceptions.JadxRuntimeException;
-
 import java.io.BufferedInputStream;
 import java.io.Closeable;
 import java.io.File;
@@ -18,10 +16,14 @@ import java.util.jar.JarOutputStream;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
+import org.apache.commons.io.IOCase;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import jadx.core.utils.exceptions.JadxRuntimeException;
+
 public class FileUtils {
 	private static final Logger LOG = LoggerFactory.getLogger(FileUtils.class);
 
@@ -43,12 +45,19 @@ public class FileUtils {
 	}
 
 	public static void makeDirsForFile(File file) {
-		File dir = file.getParentFile();
-		if (dir != null && !dir.exists()) {
-			// if directory already created in other thread mkdirs will return false,
-			// so check dir existence again
-			if (!dir.mkdirs() && !dir.exists()) {
-				throw new JadxRuntimeException("Can't create directory " + dir);
+		if (file != null) {
+			makeDirs(file.getParentFile());
+		}
+	}
+
+	private static final Object MKDIR_SYNC = new Object();
+
+	public static void makeDirs(@Nullable File dir) {
+		if (dir != null) {
+			synchronized (MKDIR_SYNC) {
+				if (!dir.exists() && !dir.mkdirs()) {
+					throw new JadxRuntimeException("Can't create directory " + dir);
+				}
 			}
 		}
 	}
@@ -186,4 +195,32 @@ public class FileUtils {
 			}
 		}
 	}
+
+	public static boolean isCaseSensitiveFS(File testDir) {
+		if (testDir != null) {
+			File caseCheckUpper = new File(testDir, "CaseCheck");
+			File caseCheckLow = new File(testDir, "casecheck");
+			try {
+				makeDirs(testDir);
+				if (caseCheckUpper.createNewFile()) {
+					boolean caseSensitive = !caseCheckLow.exists();
+					LOG.debug("Filesystem at {} is {} case-sensitive", testDir.getAbsolutePath(),
+							(caseSensitive ? "" : "NOT"));
+					return caseSensitive;
+				} else {
+					LOG.debug("Failed to create file: {}", caseCheckUpper.getAbsolutePath());
+				}
+			} catch (Exception e) {
+				LOG.debug("Failed to detect filesystem case-sensitivity by file creation", e);
+			} finally {
+				try {
+					caseCheckUpper.delete();
+					caseCheckLow.delete();
+				} catch (Exception e) {
+					// ignore
+				}
+			}
+		}
+		return IOCase.SYSTEM.isCaseSensitive();
+	}
 }