diff --git a/.changeset/eighty-feet-sparkle.md b/.changeset/eighty-feet-sparkle.md
new file mode 100644
index 000000000..392cef7e3
--- /dev/null
+++ b/.changeset/eighty-feet-sparkle.md
@@ -0,0 +1,5 @@
+---
+'@pothos/core': patch
+---
+
+Fix duplicate interfaces when building a schema multiple times
diff --git a/packages/core/src/config-store.ts b/packages/core/src/config-store.ts
index 6e2210812..044bfa127 100644
--- a/packages/core/src/config-store.ts
+++ b/packages/core/src/config-store.ts
@@ -443,8 +443,12 @@ export default class ConfigStore<Types extends SchemaTypes> {
     this.pending = false;
 
     const fns = this.addFieldFns;
+    const interfaces = this.pendingInterfaces;
+    const unions = this.pendingUnionTypes;
 
     this.addFieldFns = [];
+    this.pendingInterfaces = new Map();
+    this.pendingUnionTypes = new Map();
 
     fns.forEach((fn) => void fn());
 
@@ -456,13 +460,13 @@ export default class ConfigStore<Types extends SchemaTypes> {
       );
     }
 
-    for (const [typeName, unionFns] of this.pendingUnionTypes) {
+    for (const [typeName, unionFns] of unions) {
       for (const fn of unionFns) {
         this.addUnionTypes(typeName, fn);
       }
     }
 
-    for (const [typeName, interfacesFns] of this.pendingInterfaces) {
+    for (const [typeName, interfacesFns] of interfaces) {
       for (const fn of interfacesFns) {
         this.addInterfaces(typeName, fn);
       }