diff --git a/classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFile.java b/classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFile.java
index 59a21ef9f..796b511a4 100644
--- a/classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFile.java
+++ b/classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFile.java
@@ -36,7 +36,8 @@ public class CVirtualFile implements VirtualFile {
 
     @Override
     public String getName() {
-        return path.substring(path.lastIndexOf('/') + 1);
+        char separatorChar = fileSystem.isWindows() ? '\\' : '/';
+        return path.substring(path.lastIndexOf(separatorChar) + 1);
     }
 
     @Override
@@ -174,7 +175,10 @@ public class CVirtualFile implements VirtualFile {
         return CFileSystem.length(chars, chars.length);
     }
 
-    private static String constructPath(String parent, String child) {
-        return parent.endsWith("/") ? parent + child : parent + "/" + child;
+    private String constructPath(String parent, String child) {
+        char separatorChar = fileSystem.isWindows() ? '\\' : '/';
+        return !parent.isEmpty() && parent.charAt(parent.length() - 1) == separatorChar
+                ? parent + child
+                : parent + separatorChar + child;
     }
 }
diff --git a/classlib/src/main/java/org/teavm/classlib/java/io/TFile.java b/classlib/src/main/java/org/teavm/classlib/java/io/TFile.java
index dc1bcec1f..31bba071a 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/io/TFile.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/io/TFile.java
@@ -411,25 +411,37 @@ public class TFile implements Serializable, Comparable<TFile> {
     public boolean mkdirs() {
         String path = getCanonicalPathImpl();
 
-        int i = path.indexOf(separatorChar);
-        if (i < 0) {
+        if (path.indexOf(separatorChar) < 0) {
             return false;
         }
+        int i = path.length();
+
+        do {
+            VirtualFile file = fs().getFile(path.substring(0, i));
+            if (file.isDirectory()) {
+                break;
+            } else if (file.isFile()) {
+                return false;
+            }
+
+            i = path.lastIndexOf(separatorChar, i - 1);
+        } while (i >= 0);
+
         i++;
+
         while (i < path.length()) {
             int next = path.indexOf(separatorChar, i);
             if (next < 0) {
                 next = path.length();
             }
-
-            VirtualFile parent = fs().getFile(path.substring(0, i));
-            if (!parent.createDirectory(path.substring(i, next))) {
-                VirtualFile child = fs().getFile(path.substring(0, next));
-                if (!child.isDirectory()) {
-                    return false;
-                }
+            if (next == i + 1) {
+                break;
             }
 
+            VirtualFile file = fs().getFile(path.substring(0, i));
+            if (!file.createDirectory(path.substring(i, next))) {
+                return false;
+            }
             i = next + 1;
         }
 
diff --git a/tools/junit/src/main/java/org/teavm/junit/CRunStrategy.java b/tools/junit/src/main/java/org/teavm/junit/CRunStrategy.java
index 983ab31a9..08cfe4489 100644
--- a/tools/junit/src/main/java/org/teavm/junit/CRunStrategy.java
+++ b/tools/junit/src/main/java/org/teavm/junit/CRunStrategy.java
@@ -119,6 +119,11 @@ class CRunStrategy implements TestRunStrategy {
                 }
                 lines.add(line);
                 stdout.add(line);
+                if (lines.size() > 10000) {
+                    output.addAll(lines);
+                    process.destroy();
+                    return false;
+                }
             }
         } catch (IOException e) {
             // do nothing