Index: test/lisp/abcl/java-tests.lisp
===================================================================
--- test/lisp/abcl/java-tests.lisp	(revision 14686)
+++ test/lisp/abcl/java-tests.lisp	(working copy)
@@ -203,6 +203,11 @@
   (jcall "offsetByCodePoints" "foobar" 0 #\Nul)
   0)
 
+(deftest jcall.7
+  (signals-error (jcall "offsetByCodePoints" "foobar" 0 nil)
+                 #+abcl    'java-exception
+                 #+allegro 'jlinker-error))
+
 (deftest jfield.1
   (type-of (jfield "java.lang.Integer" "TYPE"))
   #+abcl    java-object
Index: src/org/armedbear/lisp/Java.java
===================================================================
--- src/org/armedbear/lisp/Java.java	(revision 14686)
+++ src/org/armedbear/lisp/Java.java	(working copy)
@@ -1065,7 +1065,9 @@
         for (int i = 0; i < methodTypes.length; ++i) {
             Class<?> methodType = methodTypes[i];
             Object arg = args[i];
-            if (!isAssignable(arg.getClass(), methodType)) {
+            if (arg == null) {
+                return !methodType.isPrimitive();
+            } else if (!isAssignable(arg.getClass(), methodType)) {
                 return false;
             }
         }