diff --git a/abi.js b/abi.js
index f41d0cb..102f915 100644
--- a/abi.js
+++ b/abi.js
@@ -41,13 +41,15 @@ export async function getAbi(className) {
     let found = abi[className]
     if (found === undefined) {
         console.log('warning: loading ABI from filesystem for '+className)
-        // const data = await readFile(ABI_BASE_PATH + `/${className}.sol/${className}.json`)
-        let data
-        try {
-            data = await readFile(ABI_BASE_PATH + `/I${className}.sol/I${className}.json`)
-        }
-        catch (e) {
-            data = await readFile(ABI_BASE_PATH + `/${className}.sol/${className}.json`)
+        let data = await readFile(ABI_BASE_PATH + `/${className}.sol/${className}.json`)
+        // Tricky code to handle proxy Vault where interface file is needed instead of class file
+        if (className == 'Vault') {
+            try {
+                data = await readFile(ABI_BASE_PATH + `/I${className}.sol/I${className}.json`)
+            }
+            catch (e) {
+                if (e.code !== 'ENOENT') throw e;
+            }    
         }
         found = JSON.parse(data.toString())['abi']
         abi[className] = found