diff --git a/packages/playwright-core/src/server/firefox/firefox.ts b/packages/playwright-core/src/server/firefox/firefox.ts
index 610ff56ab9..38c6db85d3 100644
--- a/packages/playwright-core/src/server/firefox/firefox.ts
+++ b/packages/playwright-core/src/server/firefox/firefox.ts
@@ -46,6 +46,12 @@ export class Firefox extends BrowserType {
   _amendEnvironment(env: Env, userDataDir: string, executable: string, browserArguments: string[]): Env {
     if (!path.isAbsolute(os.homedir()))
       throw new Error(`Cannot launch Firefox with relative home directory. Did you set ${os.platform() === 'win32' ? 'USERPROFILE' : 'HOME'} to a relative path?`);
+    if (os.platform() === 'linux') {
+      // Always remove SNAP_NAME and SNAP_INSTANCE_NAME env variables since they
+      // confuse Firefox: in our case, builds never come from SNAP.
+      // See https://github.com/microsoft/playwright/issues/20555
+      return { ...env, SNAP_NAME: undefined, SNAP_INSTANCE_NAME: undefined };
+    }
     return env;
   }