diff --git a/com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/BitwiseFunctions.java b/com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/BitwiseFunctions.java
index dc67759ab247512bf3874f8bb7d12c843877287b..6f8b4034f27b6222cb8a6a4359c65c82bcf71d22 100644
--- a/com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/BitwiseFunctions.java
+++ b/com.oracle.truffle.r.nodes.builtin/src/com/oracle/truffle/r/nodes/builtin/base/BitwiseFunctions.java
@@ -91,14 +91,14 @@ public class BitwiseFunctions {
                             v = aVal ^ bVal;
                             break;
                         case SHIFTR:
-                            if (bVal > 31) {
+                            if (bVal > 31 || bVal < 0) {
                                 v = RRuntime.INT_NA;
                             } else {
                                 v = aVal >>> bVal;
                             }
                             break;
                         case SHIFTL:
-                            if (bVal > 31) {
+                            if (bVal > 31 || bVal < 0) {
                                 v = RRuntime.INT_NA;
                             } else {
                                 v = aVal << bVal;
diff --git a/documentation/graphics.md b/documentation/graphics.md
index e940d16f39881787e71e3142786bacf1fd341b61..8cd2bfb9a4fa981c99f8ea45bd98b4c41523247a 100644
--- a/documentation/graphics.md
+++ b/documentation/graphics.md
@@ -94,3 +94,4 @@ FastR's grid implementation does not yet support:
 
 FastR does not plan to implement the R graphics engine display list
 and related functions. However, the grid display list is implemented.
+