diff --git a/types/theme-ui/index.d.ts b/types/theme-ui/index.d.ts
index 9291c22bc7..5db03511ff 100644
--- a/types/theme-ui/index.d.ts
+++ b/types/theme-ui/index.d.ts
@@ -3,6 +3,7 @@
 // Definitions by: Erik Stockmeier <https://github.com/erikdstock>
 //                 Ifiok Jr. <https://github.com/ifiokjr>
 //                 Brian Andrews <https://github.com/sbardian>
+//                 Rodrigo Pombo <https://github.com/pomber>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 3.1
 
@@ -111,7 +112,7 @@ export interface Theme extends StyledSystemTheme {
      * fonts, etc.
      */
     styles?: {
-        [P in StyledTags]: SystemStyleObject;
+        [P in StyledTags]?: SystemStyleObject;
     };
 }
 
diff --git a/types/theme-ui/theme-ui-tests.tsx b/types/theme-ui/theme-ui-tests.tsx
index c274f3dda0..fd638df2c2 100644
--- a/types/theme-ui/theme-ui-tests.tsx
+++ b/types/theme-ui/theme-ui-tests.tsx
@@ -96,3 +96,19 @@ const incompleteThemeColorModes: Theme = {
         },
     },
 };
+
+const themeWithStyles: Theme = {
+    colors: {
+        text: '#000',
+        background: '#fff',
+        primary: '#07c',
+    },
+    styles: {
+        h1: {
+            fontSize: 32,
+            color: 'primary',
+            mt: 4,
+            mb: 2,
+        },
+    },
+};