gistfile1.diff

diff --git a/core/src/main/java/org/jruby/RubyInstanceConfig.java b/core/src/main/java/org/jruby/RubyInstanceConfig.java
index 02b580b..9a8a1e4 100644
--- a/core/src/main/java/org/jruby/RubyInstanceConfig.java
+++ b/core/src/main/java/org/jruby/RubyInstanceConfig.java
@@ -1865,7 +1865,8 @@ public class RubyInstanceConfig {
         } else if (specDecimal.compareTo(BIGDECIMAL_1_5) >= 0) {
             return Opcodes.V1_5;
         } else {
-            throw new RuntimeException("unsupported Java version: " + specVersion);
+            System.err.println("unsupported Java version \"" + specVersion + "\", defaulting to 1.5");
+            return Opcodes.V1_5;
         }
     }
 
diff --git a/core/src/main/java/org/jruby/compiler/impl/StandardASMCompiler.java b/core/src/main/java/org/jruby/compiler/impl/StandardASMCompiler.java
index ddb0002..4622e62 100644
--- a/core/src/main/java/org/jruby/compiler/impl/StandardASMCompiler.java
+++ b/core/src/main/java/org/jruby/compiler/impl/StandardASMCompiler.java
@@ -520,11 +520,21 @@ public class StandardASMCompiler implements ScriptCompiler, Opcodes {
             SkinnyMethodAdapter method = new SkinnyMethodAdapter(getClassVisitor(), ACC_PUBLIC | ACC_STATIC, "main", sig(Void.TYPE, params(String[].class)), null, null);
             method.start();
 
+            // init script filename to simple class name in case we don't assign it (null ClassLoader)
+            method.ldc(getClassname().replaceAll("\\\\.", "/"));
+            method.astore(1);
+
             // new instance to invoke run against
             method.newobj(getClassname());
             method.dup();
             method.invokespecial(getClassname(), "<init>", sig(Void.TYPE));
 
+            // guard against null classloader
+            method.ldc(Type.getType("L" + getClassname() + ";"));
+            method.invokevirtual(p(Class.class), "getClassLoader", sig(ClassLoader.class));
+            Label skip = new Label();
+            method.ifnull(skip);
+
             // set filename for the loaded script class (JRUBY-4825)
             method.dup();
             method.ldc(Type.getType("L" + getClassname() + ";"));
@@ -536,6 +546,9 @@ public class StandardASMCompiler implements ScriptCompiler, Opcodes {
             method.aload(1);
             method.invokevirtual(p(AbstractScript.class), "setFilename", sig(void.class, String.class));
 
+            // ifnull ClassLoader
+            method.label(skip);
+
             // instance config for the script run
             method.newobj(p(RubyInstanceConfig.class));
             method.dup();