diff --git a/.changeset/strange-dingos-confess.md b/.changeset/strange-dingos-confess.md
new file mode 100644
index 0000000000..d6d778d4f8
--- /dev/null
+++ b/.changeset/strange-dingos-confess.md
@@ -0,0 +1,5 @@
+---
+'graphql-tool-utilities': patch
+---
+
+Fix import of apollo-codegen-core when using the mjs version of the package
diff --git a/packages/graphql-tool-utilities/src/ast.ts b/packages/graphql-tool-utilities/src/ast.ts
index fa216f081d..d4d374b412 100644
--- a/packages/graphql-tool-utilities/src/ast.ts
+++ b/packages/graphql-tool-utilities/src/ast.ts
@@ -8,7 +8,8 @@ import type {
   LegacyInlineFragment,
   LegacyOperation,
 } from 'apollo-codegen-core/lib/compiler/legacyIR';
-import {compileToLegacyIR as compileToIR} from 'apollo-codegen-core/lib/compiler/legacyIR';
+// Explicit js extension as it is required for the esm build
+import {compileToLegacyIR as compileToIR} from 'apollo-codegen-core/lib/compiler/legacyIR.js';
 
 export enum OperationType {
   Query = 'query',