diff --git a/toolkit/crashreporter/google-breakpad/src/client/linux/crash_generation/client_info.h b/toolkit/crashreporter/google-breakpad/src/client/linux/crash_generation/client_info.h
index dde2c89e1c78..11deee126fd8 100644
--- a/toolkit/crashreporter/google-breakpad/src/client/linux/crash_generation/client_info.h
+++ b/toolkit/crashreporter/google-breakpad/src/client/linux/crash_generation/client_info.h
@@ -32,6 +32,8 @@
 
 namespace google_breakpad {
 
+class CrashGenerationServer;
+
 struct ClientInfo {
   CrashGenerationServer* crash_server_;
   pid_t pid_;