diff --git a/openbsc/src/libbsc/system_information.c b/openbsc/src/libbsc/system_information.c
index 6c601e4..3d55d1a 100644
--- a/openbsc/src/libbsc/system_information.c
+++ b/openbsc/src/libbsc/system_information.c
@@ -149,7 +149,7 @@
 }
 
 /* 3GPP TS 44.018, Table 9.1.54.1 - prepend diversity bit to scrambling code */
-uint16_t encode_fdd(uint16_t scramble, bool diversity)
+static inline uint16_t encode_fdd(uint16_t scramble, bool diversity)
 {
 	if (diversity)
 		return scramble | (1 << 9);