diff --git a/com.oracle.truffle.r.test.native/urand/src/Makefile b/com.oracle.truffle.r.test.native/urand/src/Makefile
index e78bd38380ee1d53af60549bb2e95f9349effe76..cf4d81e20d95b39354845957325af4aee174b1a9 100644
--- a/com.oracle.truffle.r.test.native/urand/src/Makefile
+++ b/com.oracle.truffle.r.test.native/urand/src/Makefile
@@ -37,13 +37,16 @@ endif
 
 INCLUDE_DIR := $(subst test.native,native,$(TOPDIR))/include
 
-all: $(C_OBJECTS)
+all: mkbin $(C_OBJECTS)
 ifneq ($(shell uname), Darwin)
 	gcc -fPIC -shared -o $(C_LIB) $(C_OBJECTS)
 else
 	gcc -dynamiclib -undefined dynamic_lookup -o $(C_LIB) $(C_OBJECTS)
 endif
 
+mkbin:
+	mkdir -p $(BIN)
+
 $(BIN)/%.o: %.c
 	gcc -I$(INCLUDE_DIR) -fPIC -O2 -c $< -o $@
 
diff --git a/com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/rffi/TestUserRNG.java b/com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/rffi/TestUserRNG.java
index e82cd897e99ceb7018f5ab8e6f1a3f02cba7216a..bca4effc45e15e8b4b535384c139f236a0a45bfc 100644
--- a/com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/rffi/TestUserRNG.java
+++ b/com.oracle.truffle.r.test/src/com/oracle/truffle/r/test/rffi/TestUserRNG.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2014, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,8 +27,14 @@ import java.nio.file.*;
 import org.junit.*;
 
 import com.oracle.truffle.r.runtime.*;
+import com.oracle.truffle.r.runtime.ffi.*;
 import com.oracle.truffle.r.test.*;
 
+/**
+ * Test for a user-defined random number generator. Implicitly tests {@code dyn.load} as well as the
+ * {@link UserRngRFFI} interface. We take care to use relative paths so the expected output file is
+ * portable.
+ */
 public class TestUserRNG extends TestBase {
     @Test
     public void testUserRNG() {