diff --git a/packages/core/src/config.ts b/packages/core/src/config.ts
index cbb2d92966..33b6c4f2ea 100644
--- a/packages/core/src/config.ts
+++ b/packages/core/src/config.ts
@@ -171,28 +171,22 @@ export function resolveConfig<Theme extends object = object>(
 export function mergeConfigs<Theme extends object = object>(
   configs: UserConfig<Theme>[],
 ): UserConfig<Theme> {
-  function getMerged<T extends 'rules' | 'variants' | 'extractors' | 'shortcuts' | 'preflights' | 'preprocess' | 'postprocess' | 'extendTheme' | 'safelist' | 'separators' | 'presets'>(key: T): ToArray<Required<UserConfig<Theme>>[T]> {
-    return uniq(configs.flatMap(p => toArray(p[key] || []) as any[])) as any
-  }
-
-  const merged = Object.assign(
-    {},
-    ...configs,
-    {
-      theme: mergeThemes(configs.map(c => c.theme)),
-      presets: getMerged('presets'),
-      safelist: getMerged('safelist'),
-      preprocess: getMerged('preprocess'),
-      postprocess: getMerged('postprocess'),
-      preflights: getMerged('preflights'),
-      rules: getMerged('rules'),
-      variants: getMerged('variants'),
-      shortcuts: getMerged('shortcuts'),
-      extractors: getMerged('extractors'),
-    },
-  )
-
-  return merged
+  const maybeArrays = ['shortcuts', 'preprocess', 'postprocess']
+  const config = configs.map(config => Object.entries(config)
+    .reduce<UserConfig<Theme>>((acc, [key, value]) => ({
+      ...acc,
+      [key]: maybeArrays.includes(key) ? toArray(value) : value,
+    }), {}))
+    .reduce<UserConfig<Theme>>(({ theme: themeA, ...a }, { theme: themeB, ...b }) => {
+      const c = mergeDeep<UserConfig<Theme>>(a, b, true)
+
+      if (themeA || themeB)
+        c.theme = mergeThemes([themeA, themeB])
+
+      return c
+    }, {})
+
+  return config
 }
 
 function mergeThemes<Theme extends object = object>(themes: (Theme | undefined)[]): Theme {
diff --git a/test/config.test.ts b/test/config.test.ts
index 7f012d38e5..4efea81bfb 100644
--- a/test/config.test.ts
+++ b/test/config.test.ts
@@ -153,13 +153,6 @@ describe('mergeConfigs', () => {
     ]))
       .toMatchInlineSnapshot(`
         {
-          "extractors": [],
-          "postprocess": [],
-          "preflights": [],
-          "preprocess": [],
-          "presets": [],
-          "rules": [],
-          "safelist": [],
           "shortcuts": [
             {
               "foo": "string",
@@ -172,8 +165,6 @@ describe('mergeConfigs', () => {
               [Function],
             ],
           ],
-          "theme": {},
-          "variants": [],
         }
       `)
   })
@@ -182,6 +173,7 @@ describe('mergeConfigs', () => {
       {
         theme: {
           fontSize: {
+            sm: ['0.875rem', '1.125rem'],
             md: ['1.125rem', '1.5rem'],
             lg: ['1.25rem', '1.5rem'],
           },
@@ -190,21 +182,14 @@ describe('mergeConfigs', () => {
       {
         theme: {
           fontSize: {
-            sm: ['0.875rem', '1.125rem'],
+            sm: ['1rem', '1.125rem'],
+            xl: ['1.5rem', '1.75rem'],
           },
         },
       },
     ]))
       .toMatchInlineSnapshot(`
         {
-          "extractors": [],
-          "postprocess": [],
-          "preflights": [],
-          "preprocess": [],
-          "presets": [],
-          "rules": [],
-          "safelist": [],
-          "shortcuts": [],
           "theme": {
             "fontSize": {
               "lg": [
@@ -216,12 +201,15 @@ describe('mergeConfigs', () => {
                 "1.5rem",
               ],
               "sm": [
-                "0.875rem",
+                "1rem",
                 "1.125rem",
               ],
+              "xl": [
+                "1.5rem",
+                "1.75rem",
+              ],
             },
           },
-          "variants": [],
         }
       `)
   })