diff --git a/core/src/main/java/org/jruby/RubyMarshal.java b/core/src/main/java/org/jruby/RubyMarshal.java
index 49d8b96f80c..55181fa9084 100644
--- a/core/src/main/java/org/jruby/RubyMarshal.java
+++ b/core/src/main/java/org/jruby/RubyMarshal.java
@@ -124,7 +124,7 @@ private static void setBinmodeIfPossible(ThreadContext context, IRubyObject io)
     public static IRubyObject load(ThreadContext context, IRubyObject recv, IRubyObject[] args, Block unusedBlock) {
         Ruby runtime = context.runtime;
         IRubyObject in = args[0];
-        IRubyObject proc = args.length == 2 ? args[1] : null;
+        IRubyObject proc = args.length == 2 ? args[1] : context.nil;
         
         try {
             InputStream rawInput;
diff --git a/core/src/main/java/org/jruby/runtime/marshal/UnmarshalStream.java b/core/src/main/java/org/jruby/runtime/marshal/UnmarshalStream.java
index 7c9acaf893c..b90f6cc52d9 100644
--- a/core/src/main/java/org/jruby/runtime/marshal/UnmarshalStream.java
+++ b/core/src/main/java/org/jruby/runtime/marshal/UnmarshalStream.java
@@ -77,6 +77,10 @@ public class UnmarshalStream extends InputStream {
     private final boolean taint;
 
     public UnmarshalStream(Ruby runtime, InputStream in, IRubyObject proc, boolean taint) throws IOException {
+        assert runtime != null;
+        assert in != null;
+        assert proc != null;
+        
         this.runtime = runtime;
         this.cache = new UnmarshalCache(runtime);
         this.proc = proc;
@@ -181,7 +185,7 @@ private static RubyModule getConstantFromPath(Ruby runtime, String path) {
     }
 
     private IRubyObject doCallProcForLink(IRubyObject result, int type) {
-        if (proc != null && type != ';') {
+        if (!proc.isNil() && type != ';') {
             // return the result of the proc, but not for symbols
             return Helpers.invoke(getRuntime().getCurrentContext(), proc, "call", result);
         }
@@ -189,7 +193,7 @@ private IRubyObject doCallProcForLink(IRubyObject result, int type) {
     }
 
     private IRubyObject doCallProcForObj(IRubyObject result) {
-        if (proc != null) {
+        if (!proc.isNil()) {
             // return the result of the proc, but not for symbols
             return Helpers.invoke(getRuntime().getCurrentContext(), proc, "call", result);
         }