diff --git a/backend/src/api/common.ts b/backend/src/api/common.ts
index 358a98c98..af93b9622 100644
--- a/backend/src/api/common.ts
+++ b/backend/src/api/common.ts
@@ -263,8 +263,13 @@ export class Common {
         case 'v0_p2wsh': flags |= TransactionFlags.p2wsh; break;
         case 'v1_p2tr': {
           flags |= TransactionFlags.p2tr;
-          if (vin.witness.length > 2) {
-            const asm = vin.inner_witnessscript_asm || transactionUtils.convertScriptSigAsm(vin.witness[vin.witness.length - 2]);
+          // in taproot, if the last witness item begins with 0x50, it's an annex
+          const hasAnnex = vin.witness?.[vin.witness.length - 1].startsWith('50');
+          // script spends have more than one witness item, not counting the annex (if present)
+          if (vin.witness.length > (hasAnnex ? 2 : 1)) {
+            // the script itself is the second-to-last witness item, not counting the annex
+            const asm = vin.inner_witnessscript_asm || transactionUtils.convertScriptSigAsm(vin.witness[vin.witness.length - (hasAnnex ? 3 : 2)]);
+            // inscriptions smuggle data within an 'OP_0 OP_IF ... OP_ENDIF' envelope
             if (asm?.includes('OP_0 OP_IF')) {
               flags |= TransactionFlags.inscription;
             }