diff --git a/com.oracle.truffle.r.native/fficall/jni/src/alloc.c b/com.oracle.truffle.r.native/fficall/jni/src/alloc.c
index 26e4e143191431ff5dc58906a036f64aaf0df3cf..d974d45d9cb5c6acae7a3864eeda99ecad9fd0ad 100644
--- a/com.oracle.truffle.r.native/fficall/jni/src/alloc.c
+++ b/com.oracle.truffle.r.native/fficall/jni/src/alloc.c
@@ -10,6 +10,7 @@
  * All rights reserved.
  */
 #include "rffiutils.h"
+#include <stdlib.h>
 
 void init_alloc(JNIEnv *env) {
 
diff --git a/com.oracle.truffle.r.native/fficall/jni/src/rf_functions.c b/com.oracle.truffle.r.native/fficall/jni/src/rf_functions.c
index b48dedce9171f8a05d11bf10e4489f983215cd04..c1dc500ba84f4cbf79687f045b2640f8c666cbf2 100644
--- a/com.oracle.truffle.r.native/fficall/jni/src/rf_functions.c
+++ b/com.oracle.truffle.r.native/fficall/jni/src/rf_functions.c
@@ -21,6 +21,7 @@
  * questions.
  */
 #include "rffiutils.h"
+#include <string.h>
 
 // Most of the functions with a Rf_ prefix
 // TODO Lots missing yet
@@ -151,12 +152,12 @@ SEXP Rf_install(const char *name) {
 
 Rboolean Rf_isNull(SEXP s) {
 	JNIEnv *thisenv = getEnv();
-	return (*thisenv)->CallStaticObjectMethod(thisenv, CallRFFIHelperClass, Rf_isNullMethodID, s);
+	return (*thisenv)->CallStaticIntMethod(thisenv, CallRFFIHelperClass, Rf_isNullMethodID, s);
 }
 
 Rboolean Rf_isString(SEXP s) {
 	JNIEnv *thisenv = getEnv();
-	return (*thisenv)->CallStaticObjectMethod(thisenv, CallRFFIHelperClass, Rf_isStringMethodID, s);
+	return (*thisenv)->CallStaticIntMethod(thisenv, CallRFFIHelperClass, Rf_isStringMethodID, s);
 
 }
 
diff --git a/com.oracle.truffle.r.native/fficall/jni/src/rffiutils.h b/com.oracle.truffle.r.native/fficall/jni/src/rffiutils.h
index 9dfcd2cd8dd90333720f5b4b18929ffb1e4cedff..50442915454adb8e965b1b0ae08a2012b29170aa 100644
--- a/com.oracle.truffle.r.native/fficall/jni/src/rffiutils.h
+++ b/com.oracle.truffle.r.native/fficall/jni/src/rffiutils.h
@@ -47,6 +47,8 @@ void init_typecoerce(JNIEnv *env);
 void init_attrib(JNIEnv *env);
 void init_misc(JNIEnv *env);
 void init_vectoraccess(JNIEnv *env);
+void init_listaccess(JNIEnv *env);
+void init_utils(JNIEnv *env);
 
 extern jclass RDataFactoryClass;
 extern jclass CallRFFIHelperClass;