diff --git a/types/rebass/index.d.ts b/types/rebass/index.d.ts
index a80ae35fcc..27b49e568f 100644
--- a/types/rebass/index.d.ts
+++ b/types/rebass/index.d.ts
@@ -6,6 +6,7 @@
 //                 sara f-p <https://github.com/gretzky>
 //                 angusfretwell <https://github.com/angusfretwell>
 //                 orzarchi <https://github.com/orzarchi>
+//                 ilaiwi <https://github.com/ilaiwi>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 3.1
 
@@ -31,7 +32,7 @@ export interface BaseProps extends React.RefAttributes<any> {
  * such that properties that are part of the `Theme` will be transformed to
  * their corresponding values. Other valid CSS properties are also allowed.
  */
-export type SxStyleProp = SystemStyleObject &
+export type SxStyleProp = SystemStyleObject |
     Record<
         string,
         | SystemStyleObject
diff --git a/types/rebass/rebass-tests.tsx b/types/rebass/rebass-tests.tsx
index 6287885ca7..f1dc0858d6 100644
--- a/types/rebass/rebass-tests.tsx
+++ b/types/rebass/rebass-tests.tsx
@@ -75,7 +75,13 @@ export default () => (
             >
                 String css prop
             </Box>
-
+            <Button sx={theme => ({
+                bg: "magenta",
+                border: "1em",
+                borderRadius: "1em"
+            })}>
+                Button
+            </Button>
             <CssBox />
         </Flex>
     </Box>