diff --git a/.changeset/proud-shrimps-try.md b/.changeset/proud-shrimps-try.md
new file mode 100644
index 00000000..123750eb
--- /dev/null
+++ b/.changeset/proud-shrimps-try.md
@@ -0,0 +1,5 @@
+---
+'@hono/zod-openapi': patch
+---
+
+chore: lock zod-to-openapi to `^7.3.0` to fix `z.custom`
diff --git a/packages/zod-openapi/package.json b/packages/zod-openapi/package.json
index 51e32a32..f8871719 100644
--- a/packages/zod-openapi/package.json
+++ b/packages/zod-openapi/package.json
@@ -52,7 +52,7 @@
     "zod": "^3.22.1"
   },
   "dependencies": {
-    "@asteasolutions/zod-to-openapi": "^7.1.0",
+    "@asteasolutions/zod-to-openapi": "^7.3.0",
     "@hono/zod-validator": "workspace:^"
   },
   "engines": {
diff --git a/yarn.lock b/yarn.lock
index 1174ff11..b83e3373 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -99,7 +99,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@asteasolutions/zod-to-openapi@npm:^7.1.0":
+"@asteasolutions/zod-to-openapi@npm:^7.3.0":
   version: 7.3.0
   resolution: "@asteasolutions/zod-to-openapi@npm:7.3.0"
   dependencies:
@@ -2363,7 +2363,7 @@ __metadata:
   resolution: "@hono/zod-openapi@workspace:packages/zod-openapi"
   dependencies:
     "@arethetypeswrong/cli": "npm:^0.17.4"
-    "@asteasolutions/zod-to-openapi": "npm:^7.1.0"
+    "@asteasolutions/zod-to-openapi": "npm:^7.3.0"
     "@hono/zod-validator": "workspace:^"
     publint: "npm:^0.3.9"
     tsup: "npm:^8.4.0"