diff --git a/.changeset/eleven-spiders-wonder.md b/.changeset/eleven-spiders-wonder.md
new file mode 100644
index 0000000..49b693d
--- /dev/null
+++ b/.changeset/eleven-spiders-wonder.md
@@ -0,0 +1,5 @@
+---
+"better-auth-convex": patch
+---
+
+fix: map Convex table names to Better Auth model keys in isUniqueField
diff --git a/src/adapterUtils.ts b/src/adapterUtils.ts
index 3efc3ea..938749a 100644
--- a/src/adapterUtils.ts
+++ b/src/adapterUtils.ts
@@ -62,14 +62,20 @@ const isUniqueField = (
   model: string,
   field: string
 ) => {
-  const fields =
-    betterAuthSchema[model as keyof typeof betterAuthSchema].fields;
-
-  if (!fields) {
+  // Map Convex table name (e.g., "users") to Better Auth model key (e.g., "user")
+  // by finding the key where betterAuthSchema[key].modelName === model
+  const betterAuthModel =
+    Object.keys(betterAuthSchema).find(
+      (key) => betterAuthSchema[key as keyof typeof betterAuthSchema].modelName === model
+    ) || model;
+  const modelSchema =
+    betterAuthSchema[betterAuthModel as keyof typeof betterAuthSchema];
+
+  if (!modelSchema?.fields) {
     return false;
   }
 
-  return Object.entries(fields)
+  return Object.entries(modelSchema.fields)
     .filter(([, value]) => value.unique)
     .map(([key]) => key)
     .includes(field);