diff --git a/R/method-ops.R b/R/method-ops.R
index a39ee00b..0617940c 100644
--- a/R/method-ops.R
+++ b/R/method-ops.R
@@ -17,11 +17,16 @@ on_load_define_ops <- function() {
 #' @export
 Ops.S7_object <- function(e1, e2) {
   cnd <- tryCatch(
-    return(base_ops[[.Generic]](e1, e2)),
+    return(
+      if (missing(e2))
+        base_ops[[.Generic]](e1)
+      else
+        base_ops[[.Generic]](e1, e2)
+    ),
     S7_error_method_not_found = function(cnd) cnd
   )
 
-  if (S7_inherits(e1) && S7_inherits(e2)) {
+  if (S7_inherits(e1) && (missing(e2) || S7_inherits(e2))) {
     stop(cnd)
   } else {
     # Must call NextMethod() directly in the method, not wrapped in an
diff --git a/tests/testthat/test-method-ops.R b/tests/testthat/test-method-ops.R
index d825b65e..2dfd1fec 100644
--- a/tests/testthat/test-method-ops.R
+++ b/tests/testthat/test-method-ops.R
@@ -122,3 +122,13 @@ test_that("Ops methods can use super", {
 
   expect_equal(foo2(1L) + 1, foo2(2L))
 })
+
+
+test_that("Unary Ops methods work", {
+  Double := new_class(class_double)
+  method(`-`, list(Double, class_missing)) <- function(e1, e2) {
+    Double(-as.double(e1))
+  }
+
+  expect_identical(-Double(1), Double(-1))
+})