diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 0f28ba0..2965afa 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
Binary files differ
diff --git a/src/version.c b/src/version.c
index 547d6a7..23d4936 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1436,
+/**/
     1435,
 /**/
     1434,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 18cebdb..d558ca0 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -3496,7 +3496,15 @@
 	    case ISN_LOAD:
 		if (GA_GROW_FAILS(&ectx->ec_stack, 1))
 		    goto theend;
-		copy_tv(STACK_TV_VAR(iptr->isn_arg.number), STACK_TV_BOT(0));
+		tv = STACK_TV_VAR(iptr->isn_arg.number);
+		if (tv->v_type == VAR_UNKNOWN)
+		{
+		    // missing argument or default value v:none
+		    STACK_TV_BOT(0)->v_type = VAR_SPECIAL;
+		    STACK_TV_BOT(0)->vval.v_number = VVAL_NONE;
+		}
+		else
+		    copy_tv(tv, STACK_TV_BOT(0));
 		++ectx->ec_stack.ga_len;
 		break;
 
diff --git a/src/vim9instr.c b/src/vim9instr.c
index e2cdc3a..52402c1 100644
--- a/src/vim9instr.c
+++ b/src/vim9instr.c
@@ -413,7 +413,7 @@
  */
     static isntype_T
 get_compare_isn(
-	exprtype_T exprtype,
+	exprtype_T  exprtype,
 	typval_T    *tv1,
 	typval_T    *tv2,
 	type_T	    *type1,
@@ -485,13 +485,17 @@
 	return ISN_DROP;
     }
     if (isntype == ISN_DROP
-	    || ((exprtype != EXPR_EQUAL && exprtype != EXPR_NEQUAL
-		    && (vartype1 == VAR_BOOL || vartype1 == VAR_SPECIAL
-		       || vartype2 == VAR_BOOL || vartype2 == VAR_SPECIAL)))
-	    || ((exprtype != EXPR_EQUAL && exprtype != EXPR_NEQUAL
-			       && exprtype != EXPR_IS && exprtype != EXPR_ISNOT
-		    && (vartype1 == VAR_BLOB || vartype2 == VAR_BLOB
-			|| vartype1 == VAR_LIST || vartype2 == VAR_LIST))))
+	    || (isntype != ISN_COMPARENULL
+		&& (((exprtype != EXPR_EQUAL
+			&& exprtype != EXPR_NEQUAL
+			&& (vartype1 == VAR_BOOL || vartype1 == VAR_SPECIAL
+			  || vartype2 == VAR_BOOL || vartype2 == VAR_SPECIAL)))
+		    || ((exprtype != EXPR_EQUAL
+			 && exprtype != EXPR_NEQUAL
+			 && exprtype != EXPR_IS
+			 && exprtype != EXPR_ISNOT
+			 && (vartype1 == VAR_BLOB || vartype2 == VAR_BLOB
+			  || vartype1 == VAR_LIST || vartype2 == VAR_LIST))))))
     {
 	semsg(_(e_cannot_compare_str_with_str),
 		vartype_name(vartype1), vartype_name(vartype2));