diff --git a/openbsc/src/gprs/gprs_sgsn.c b/openbsc/src/gprs/gprs_sgsn.c
index 711540e..2f5d39e 100644
--- a/openbsc/src/gprs/gprs_sgsn.c
+++ b/openbsc/src/gprs/gprs_sgsn.c
@@ -183,7 +183,7 @@
 
 /* this is a hard _free_ function, it doesn't clean up the PDP contexts
  * in libgtp! */
-void sgsn_mm_ctx_free(struct sgsn_mm_ctx *mm)
+static void sgsn_mm_ctx_free(struct sgsn_mm_ctx *mm)
 {
 	struct sgsn_pdp_ctx *pdp, *pdp2;