diff --git a/conf/modules/gps_ublox.xml b/conf/modules/gps_ublox.xml
index 0ab7093e28..f8a23b40a9 100644
--- a/conf/modules/gps_ublox.xml
+++ b/conf/modules/gps_ublox.xml
@@ -18,17 +18,31 @@
   <!--periodic fun="gps_periodic_check()" freq="1." autorun="TRUE"/-->
   <!--event fun="GpsEvent(on_gps_solution)"/-->
   <makefile target="ap">
+    <configure name="UBX_GPS_PORT" default="$(GPS_PORT)" case="upper|lower"/>
+    <configure name="UBX_GPS_BAUD" default="$(GPS_BAUD)"/>
     <file name="gps.c" dir="subsystems"/>
     <file name="gps_ubx.c" dir="subsystems/gps"/>
     <define name="USE_GPS"/>
     <configure name="GPS_PORT" case="upper|lower"/>
-    <define name="USE_$(GPS_PORT_UPPER)"/>
-    <define name="GPS_LINK" value="$(GPS_PORT_LOWER)"/>
-    <define name="$(GPS_PORT_UPPER)_BAUD" value="$(GPS_BAUD)"/>
+    <define name="USE_$(UBX_GPS_PORT_UPPER)"/>
+    <define name="UBX_GPS_LINK" value="$(UBX_GPS_PORT_LOWER)"/>
+    <define name="$(UBX_GPS_PORT_UPPER)_BAUD" value="$(UBX_GPS_BAUD)"/>
     <configure name="GPS_LED" default="none"/>
     <define name="GPS_LED" value="$(GPS_LED)" cond="ifneq ($(GPS_LED),none)"/>
     <raw>
+      ifdef SECONDARY_GPS
+      ifneq (,$(findstring $(SECONDARY_GPS), ublox))
+      # this is the secondary GPS
+      ap.CFLAGS += -DGPS_SECONDARY_TYPE_H=\"subsystems/gps/gps_ubx.h\"
+      ap.CFLAGS += -DSECONDARY_GPS=gps_ubx
+      else
       ap.CFLAGS += -DGPS_TYPE_H=\"subsystems/gps/gps_ubx.h\"
+      ap.CFLAGS += -DPRIMARY_GPS=gps_ubx
+      endif
+      else
+      # plain old single GPS usage
+      ap.CFLAGS += -DGPS_TYPE_H=\"subsystems/gps/gps_ubx.h\"
+      endif
     </raw>
   </makefile>
   <makefile target="nps">