diff --git a/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum.expected b/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.expected
similarity index 97%
rename from compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum.expected
rename to compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.expected
index 97ab0b9a76d6a..083d930477691 100644
--- a/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum.expected
+++ b/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.expected
@@ -44,7 +44,7 @@ enum Status {
 ==================================== OUTPUT ===================================
 //- __generated__/SomeComponentFragment.graphql.js
 /**
- * <auto-generated> SignedSource<<5f1eb0560c62a91c8a4ca0dbf2963b85>>
+ * <auto-generated> SignedSource<<f6f0388cfc79b6eeaed86875ad2cffd1>>
  * @flow
  * @lightSyntaxTransform
  * @nogrep
@@ -57,7 +57,7 @@ enum Status {
 /*::
 import type { Fragment, ReaderFragment } from 'relay-runtime';
 import type { User____relay_model_instance$data } from "User____relay_model_instance.graphql";
-export type Status = "ADMIN" | "USER" | "%future added value";
+export type Status = "ADMIN" | "USER";
 import type { FragmentType } from "relay-runtime";
 import {status as userStatusResolverType} from "UserTypeResolvers";
 // Type assertion validating that `userStatusResolverType` resolver is correctly implemented.
diff --git a/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum.input b/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.input
similarity index 100%
rename from compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum.input
rename to compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.input
diff --git a/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum_with_enum_suffix.expected b/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum_with_enum_suffix.expected
index 619bb695dc1d2..91b6481bfe0dc 100644
--- a/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum_with_enum_suffix.expected
+++ b/compiler/crates/relay-compiler/tests/relay_compiler_integration/fixtures/resolver_returns_enum_with_enum_suffix.expected
@@ -45,7 +45,7 @@ enum Status {
 ==================================== OUTPUT ===================================
 //- __generated__/SomeComponentFragment.graphql.js
 /**
- * <auto-generated> SignedSource<<19d9d78bd05aabfe1298f8b3a0c3ae01>>
+ * <auto-generated> SignedSource<<f6f0388cfc79b6eeaed86875ad2cffd1>>
  * @flow
  * @lightSyntaxTransform
  * @nogrep
@@ -58,7 +58,7 @@ enum Status {
 /*::
 import type { Fragment, ReaderFragment } from 'relay-runtime';
 import type { User____relay_model_instance$data } from "User____relay_model_instance.graphql";
-import type { Status } from "Status.LOL_WHAT";
+export type Status = "ADMIN" | "USER";
 import type { FragmentType } from "relay-runtime";
 import {status as userStatusResolverType} from "UserTypeResolvers";
 // Type assertion validating that `userStatusResolverType` resolver is correctly implemented.
diff --git a/compiler/crates/relay-compiler/tests/relay_compiler_integration_test.rs b/compiler/crates/relay-compiler/tests/relay_compiler_integration_test.rs
index 9969b29107dd0..b0f6a7e55b890 100644
--- a/compiler/crates/relay-compiler/tests/relay_compiler_integration_test.rs
+++ b/compiler/crates/relay-compiler/tests/relay_compiler_integration_test.rs
@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @generated SignedSource<<be9e021bfe875928b8f65310c8e413a7>>
+ * @generated SignedSource<<276e2284c38de688261ae6c3a87e49ee>>
  */
 
 mod relay_compiler_integration;
@@ -139,10 +139,10 @@ async fn resolver_on_interface_returns_custom_scalar() {
 }
 
 #[tokio::test]
-async fn resolver_returns_enum() {
-    let input = include_str!("relay_compiler_integration/fixtures/resolver_returns_enum.input");
-    let expected = include_str!("relay_compiler_integration/fixtures/resolver_returns_enum.expected");
-    test_fixture(transform_fixture, file!(), "resolver_returns_enum.input", "relay_compiler_integration/fixtures/resolver_returns_enum.expected", input, expected).await;
+async fn resolver_returns_client_schema_extension_enum() {
+    let input = include_str!("relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.input");
+    let expected = include_str!("relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.expected");
+    test_fixture(transform_fixture, file!(), "resolver_returns_client_schema_extension_enum.input", "relay_compiler_integration/fixtures/resolver_returns_client_schema_extension_enum.expected", input, expected).await;
 }
 
 #[tokio::test]
diff --git a/compiler/crates/relay-typegen/src/write.rs b/compiler/crates/relay-typegen/src/write.rs
index dfb1fe1525d1c..c7f847b3b9345 100644
--- a/compiler/crates/relay-typegen/src/write.rs
+++ b/compiler/crates/relay-typegen/src/write.rs
@@ -636,16 +636,18 @@ fn write_enum_definitions(
     writer: &mut Box<dyn Writer>,
 ) -> FmtResult {
     let enum_ids = encountered_enums.into_sorted_vec(typegen_context.schema);
+    let maybe_suffix = &typegen_context
+        .project_config
+        .typegen_config
+        .enum_module_suffix;
     for enum_id in enum_ids {
         let enum_type = typegen_context.schema.enum_(enum_id);
-        if let Some(enum_module_suffix) = &typegen_context
-            .project_config
-            .typegen_config
-            .enum_module_suffix
-        {
+        if !enum_type.is_extension && maybe_suffix.is_some() {
+            // We can't chain `if let` statements, so we need to unwrap here.
+            let suffix = maybe_suffix.as_ref().unwrap();
             writer.write_import_type(
                 &[enum_type.name.item.lookup()],
-                &format!("{}{}", enum_type.name.item, enum_module_suffix),
+                &format!("{}{}", enum_type.name.item, suffix),
             )?;
         } else {
             let mut members: Vec<AST> = enum_type
@@ -654,10 +656,21 @@ fn write_enum_definitions(
                 .map(|enum_value| AST::StringLiteral(StringLiteral(enum_value.value)))
                 .collect();
 
-            if !typegen_context
-                .project_config
-                .typegen_config
-                .no_future_proof_enums
+            // Users can specify a config option to disable the inclusion of
+            // FUTURE_ENUM_VALUE in the enum union. Additionally we want to avoid
+            // emitting FUTURE_ENUM_VALUE if the enum is actually defined on the
+            // client. For example in Client Schema Extensions or (some day)
+            // Relay Resolvers.
+            //
+            // In the case of a client defined enum, we don't need to enforce
+            // the breaking change semantics dictated by the GraphQL spec
+            // because new fields added to the client schema will simply result
+            // in fixable Flow/TypeScript errors elsewhere in the codebase.
+            if !(enum_type.is_extension
+                || typegen_context
+                    .project_config
+                    .typegen_config
+                    .no_future_proof_enums)
             {
                 members.push(AST::StringLiteral(StringLiteral(*FUTURE_ENUM_VALUE)));
             }