diff --git a/.changeset/healthy-hornets-guess.md b/.changeset/healthy-hornets-guess.md
new file mode 100644
index 00000000..602a6c63
--- /dev/null
+++ b/.changeset/healthy-hornets-guess.md
@@ -0,0 +1,5 @@
+---
+'@apollo/sandbox': minor
+---
+
+adjust multipart form construction logic
diff --git a/package-lock.json b/package-lock.json
index b670060f..fcd15fa6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9987,7 +9987,7 @@
     },
     "packages/explorer": {
       "name": "@apollo/explorer",
-      "version": "3.6.0",
+      "version": "3.7.0",
       "license": "MIT",
       "dependencies": {
         "@types/whatwg-mimetype": "^3.0.0",
@@ -10033,7 +10033,7 @@
     },
     "packages/sandbox": {
       "name": "@apollo/sandbox",
-      "version": "2.5.1",
+      "version": "2.7.0",
       "license": "MIT",
       "dependencies": {
         "@types/whatwg-mimetype": "^3.0.0",
diff --git a/packages/sandbox/src/helpers/constructMultipartForm.ts b/packages/sandbox/src/helpers/constructMultipartForm.ts
index f017b704..09b47dac 100644
--- a/packages/sandbox/src/helpers/constructMultipartForm.ts
+++ b/packages/sandbox/src/helpers/constructMultipartForm.ts
@@ -57,6 +57,7 @@ export const constructMultipartForm = async ({
   let variablesWithNullsForFiles:
     | Record<string, JSONValue | undefined | null | null[]>
     | undefined = requestBody.variables;
+
   fileVariables.forEach(
     ({ files, variableKey, isMultiFile }, fileVariableIndex) => {
       if (files?.length) {
@@ -68,9 +69,7 @@ export const constructMultipartForm = async ({
         };
         Array.from(files).forEach((file) => {
           map[i] = [
-            `${
-              fileVariables.length > 1 ? `${fileVariableIndex}.` : ''
-            }variables.${variableKey}${isMultiFile ? `.${i}` : ''}`,
+            `variables.${variableKey}${isMultiFile ? `.${fileVariableIndex}` : ''}`,
           ];
           // in the request, there is expected to be a number appended that corresponds to each file
           // https://github.com/jaydenseric/graphql-multipart-request-spec#file-list