diff --git a/rhino/src/main/java/org/mozilla/classfile/ClassFileWriter.java b/rhino/src/main/java/org/mozilla/classfile/ClassFileWriter.java
index 106d0063c5..f2f7ab29aa 100644
--- a/rhino/src/main/java/org/mozilla/classfile/ClassFileWriter.java
+++ b/rhino/src/main/java/org/mozilla/classfile/ClassFileWriter.java
@@ -4367,21 +4367,31 @@ private void finalizeSuperBlockStarts() {
         // Based on the version numbers we scrape, we can also determine what
         // bytecode features we need. For example, Java 6 bytecode (classfile
         // version 50) should have stack maps generated.
+        int minor = 0;
+        int major = 48;
         try (InputStream is = readClassFile()) {
-            byte[] header = new byte[8];
-            // read loop is required since JDK7 will only provide 2 bytes
-            // on the first read() - see bug #630111
-            int read = 0;
-            while (read < 8) {
-                int c = is.read(header, read, 8 - read);
-                if (c < 0) throw new IOException();
-                read += c;
+            if (is != null) {
+                byte[] header = new byte[8];
+                // read loop is required since JDK7 will only provide 2 bytes
+                // on the first read() - see bug #630111
+                int read = 0;
+                while (read < 8) {
+                    int c = is.read(header, read, 8 - read);
+                    if (c < 0) throw new IOException();
+                    read += c;
+                }
+                minor = (header[4] << 8) | (header[5] & 0xff);
+                major = (header[6] << 8) | (header[7] & 0xff);
+            } else {
+                System.err.println(
+                        "Warning: Unable to read ClassFileWriter.class, using default bytecode version");
             }
-            MinorVersion = (header[4] << 8) | (header[5] & 0xff);
-            MajorVersion = (header[6] << 8) | (header[7] & 0xff);
-            GenerateStackMap = MajorVersion >= 50;
         } catch (IOException ioe) {
             throw new AssertionError("Can't read ClassFileWriter.class to get bytecode version");
+        } finally {
+            MinorVersion = minor;
+            MajorVersion = major;
+            GenerateStackMap = MajorVersion >= 50;
         }
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/JavaMembers.java b/rhino/src/main/java/org/mozilla/javascript/JavaMembers.java
index cefb97100f..abd9caa513 100644
--- a/rhino/src/main/java/org/mozilla/javascript/JavaMembers.java
+++ b/rhino/src/main/java/org/mozilla/javascript/JavaMembers.java
@@ -328,7 +328,8 @@ private void discoverAccessibleMethods(
                                 if (isPublic(mods) || isProtected(mods) || includePrivate) {
                                     MethodSignature sig = new MethodSignature(method);
                                     if (!map.containsKey(sig)) {
-                                        if (includePrivate) method.trySetAccessible();
+                                        if (includePrivate && !method.isAccessible())
+                                            method.setAccessible(true);
                                         map.put(sig, method);
                                     }
                                 }
@@ -667,7 +668,7 @@ private Field[] getAccessibleFields(boolean includeProtected, boolean includePri
                     for (Field field : declared) {
                         int mod = field.getModifiers();
                         if (includePrivate || isPublic(mod) || isProtected(mod)) {
-                            field.trySetAccessible();
+                            if (!field.isAccessible()) field.setAccessible(true);
                             fieldsList.add(field);
                         }
                     }