diff --git a/src/Makefile.am b/src/Makefile.am
index 1728c9e..db1f87f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -33,10 +33,17 @@
 	gsm_rlcmac.cpp \
 	gprs_bssgp_pcu.cpp \
 	gprs_rlcmac.cpp \
-	pcu_l1_if.cpp \
 	gsm_timer.cpp \
 	bitvector.cpp
 
+if ENABLE_SYSMOBTS
+libgprs_la_SOURCES += \
+	sysmo_l1_if.cpp
+else
+libgprs_la_SOURCES += \
+	pcu_l1_if.cpp
+endif
+
 noinst_PROGRAMS = \
 	RLCMACTest \
 	pcu