diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index dfdf68b9ce5584..011f67fa799913 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -171,6 +171,25 @@ void CallbackInfo::WeakCallback(Isolate* isolate, Local<Object> object) {
 }
 
 
+// Parse index for external array data.
+inline MUST_USE_RESULT bool ParseArrayIndex(Local<Value> arg,
+                                            size_t def,
+                                            size_t* ret) {
+  if (arg->IsUndefined()) {
+    *ret = def;
+    return true;
+  }
+
+  int64_t tmp_i = arg->IntegerValue();
+
+  if (tmp_i < 0)
+    return false;
+
+  *ret = static_cast<size_t>(tmp_i);
+  return true;
+}
+
+
 // Buffer methods
 
 bool HasInstance(Local<Value> val) {
diff --git a/src/node_internals.h b/src/node_internals.h
index ae1256756c31db..ef3af51018c9a0 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -160,24 +160,6 @@ inline bool IsBigEndian() {
   return GetEndianness() == kBigEndian;
 }
 
-// parse index for external array data
-inline MUST_USE_RESULT bool ParseArrayIndex(v8::Local<v8::Value> arg,
-                                            size_t def,
-                                            size_t* ret) {
-  if (arg->IsUndefined()) {
-    *ret = def;
-    return true;
-  }
-
-  int32_t tmp_i = arg->Int32Value();
-
-  if (tmp_i < 0)
-    return false;
-
-  *ret = static_cast<size_t>(tmp_i);
-  return true;
-}
-
 void ThrowError(v8::Isolate* isolate, const char* errmsg);
 void ThrowTypeError(v8::Isolate* isolate, const char* errmsg);
 void ThrowRangeError(v8::Isolate* isolate, const char* errmsg);