diff --git a/src/deploy/functions/prepare.ts b/src/deploy/functions/prepare.ts
index 60801d85158..ad8d373e367 100644
--- a/src/deploy/functions/prepare.ts
+++ b/src/deploy/functions/prepare.ts
@@ -31,7 +31,9 @@ import { AUTH_BLOCKING_EVENTS } from "../../functions/events/v1";
 import { generateServiceIdentity } from "../../gcp/serviceusage";
 import { applyBackendHashToBackends } from "./cache/applyHash";
 import { allEndpoints, Backend } from "./backend";
+import { assertExhaustive } from "../../functional";
 
+export const EVENTARC_SOURCE_ENV = "EVENTARC_CLOUD_EVENT_SOURCE";
 function hasUserConfig(config: Record<string, unknown>): boolean {
   // "firebase" key is always going to exist in runtime config.
   // If any other key exists, we can assume that user is using runtime config.
@@ -138,7 +140,19 @@ export async function prepare(
     }
 
     for (const endpoint of backend.allEndpoints(wantBackend)) {
-      endpoint.environmentVariables = wantBackend.environmentVariables;
+      endpoint.environmentVariables = wantBackend.environmentVariables || {};
+      let resource: string;
+      if (endpoint.platform === "gcfv1") {
+        resource = `projects/${endpoint.project}/locations/${endpoint.region}/functions/${endpoint.id}`;
+      } else if (endpoint.platform === "gcfv2") {
+        // N.B. If GCF starts allowing v1's allowable characters in IDs they're
+        // going to need to have a transform to create a service ID (which has a
+        // more restrictive cahracter set). We'll need to reimplement that here.
+        resource = `projects/${endpoint.project}/locations/${endpoint.region}/services/${endpoint.id}`;
+      } else {
+        assertExhaustive(endpoint.platform);
+      }
+      endpoint.environmentVariables[EVENTARC_SOURCE_ENV] = resource;
       endpoint.codebase = codebase;
     }
     wantBackends[codebase] = wantBackend;
diff --git a/src/emulator/functionsEmulatorShared.ts b/src/emulator/functionsEmulatorShared.ts
index 77155871e4f..d6414a09d45 100644
--- a/src/emulator/functionsEmulatorShared.ts
+++ b/src/emulator/functionsEmulatorShared.ts
@@ -25,6 +25,13 @@ const V2_EVENTS = [
   ...events.v2.DATABASE_EVENTS,
 ];
 
+/**
+ * Label for eventarc event sources.
+ * TODO: Consider DRYing from functions/prepare.ts
+ * A nice place would be to put it in functionsv2.ts once we get rid of functions.ts
+ */
+export const EVENTARC_SOURCE_ENV = "EVENTARC_CLOUD_EVENT_SOURCE";
+
 export type SignatureType = "http" | "event" | "cloudevent";
 
 export interface ParsedTriggerDefinition {
@@ -171,6 +178,19 @@ export function emulatedFunctionsFromEndpoints(
     };
     def.availableMemoryMb = endpoint.availableMemoryMb || 256;
     def.labels = endpoint.labels || {};
+    if (endpoint.platform === "gcfv1") {
+      def.labels[EVENTARC_SOURCE_ENV] =
+        "cloudfunctions-emulated.googleapis.com" +
+        `/projects/${endpoint.project || "project"}/locations/${endpoint.region}/functions/${
+          endpoint.id
+        }`;
+    } else if (endpoint.platform === "gcfv2") {
+      def.labels[EVENTARC_SOURCE_ENV] =
+        "run-emulated.googleapis.com" +
+        `/projects/${endpoint.project || "project"}/locations/${endpoint.region}/services/${
+          endpoint.id
+        }`;
+    }
     def.timeoutSeconds = endpoint.timeoutSeconds || 60;
     def.secretEnvironmentVariables = endpoint.secretEnvironmentVariables || [];
     def.platform = endpoint.platform;