diff --git a/client/client_state.C b/client/client_state.C
index 3dd4e2dda1..8c01564a05 100644
--- a/client/client_state.C
+++ b/client/client_state.C
@@ -74,7 +74,9 @@ CLIENT_STATE::CLIENT_STATE() {
     core_client_version.minor = BOINC_MINOR_VERSION;
     core_client_version.release = BOINC_RELEASE;
     platform_name = HOSTTYPE;
+#ifdef _WIN64
     alt_platform_name = HOSTTYPEALT;
+#endif
     exit_after_app_start_secs = 0;
     app_started = 0;
     exit_before_upload = false;
diff --git a/client/client_state.h b/client/client_state.h
index 264f5fc32a..8a10d86f81 100644
--- a/client/client_state.h
+++ b/client/client_state.h
@@ -157,7 +157,9 @@ public:
     bool run_by_updater;
     double now;
     const char* platform_name;
+#ifdef _WIN64
     const char* alt_platform_name;
+#endif
     bool initialized;
 
 private: