diff --git a/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/ArgumentsSignature.java b/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/ArgumentsSignature.java
index ecd287b87b5bdf9a1c120d634bc935e074af3c8c..6dedde1535352ed78b38f7aa66e496d2e6ccf3ad 100644
--- a/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/ArgumentsSignature.java
+++ b/com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/ArgumentsSignature.java
@@ -222,6 +222,9 @@ public final class ArgumentsSignature implements Iterable<String> {
             return false;
         }
         ArgumentsSignature other = (ArgumentsSignature) obj;
+        if (length != other.length) {
+            return false;
+        }
         if (!Arrays.equals(names, other.names)) {
             return false;
         }