diff --git a/com.oracle.truffle.r.ffi.impl/src/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Zip.java b/com.oracle.truffle.r.ffi.impl/src/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Zip.java
index b309d2d59b4292f5364fca141b5e2a82c8474cda..a3ff3980e252e40e3123e583b96f212ea031ffff 100644
--- a/com.oracle.truffle.r.ffi.impl/src/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Zip.java
+++ b/com.oracle.truffle.r.ffi.impl/src/com/oracle/truffle/r/ffi/impl/nfi/TruffleNFI_Zip.java
@@ -40,7 +40,7 @@ public class TruffleNFI_Zip implements ZipRFFI {
             try {
                 int result = (int) ForeignAccess.sendExecute(message, NFIFunction.compress.getFunction(),
                                 JavaInterop.asTruffleObject(dest), JavaInterop.asTruffleObject(destlen),
-                                JavaInterop.asTruffleObject(source), JavaInterop.asTruffleObject(source.length));
+                                JavaInterop.asTruffleObject(source), source.length);
                 return result;
             } catch (InteropException e) {
                 throw RInternalError.shouldNotReachHere(e);
@@ -57,7 +57,7 @@ public class TruffleNFI_Zip implements ZipRFFI {
             try {
                 int result = (int) ForeignAccess.sendExecute(message, NFIFunction.uncompress.getFunction(),
                                 JavaInterop.asTruffleObject(dest), JavaInterop.asTruffleObject(destlen),
-                                JavaInterop.asTruffleObject(source), JavaInterop.asTruffleObject(source.length));
+                                JavaInterop.asTruffleObject(source), source.length);
                 return result;
             } catch (InteropException e) {
                 throw RInternalError.shouldNotReachHere(e);