diff --git a/lib_com/prot.h b/lib_com/prot.h
index 87f01a916193b2d74f2caa805a05d7fce7a27002..de16bd83427632984481b1e3c0708a00a6c0d358 100644
--- a/lib_com/prot.h
+++ b/lib_com/prot.h
@@ -161,12 +161,14 @@ int16_t sum_s(
     const int16_t lvec  /* i  : length of input vector                          */
 );
 
+#ifdef DEBUGGING
 /*! r: sum of all vector elements */
 int32_t sum_l(
     const int32_t *vec, /* i  : input vector                                    */
     const int16_t lvec  /* i  : length of input vector                          */
 );
 
+#endif
 /*! r: sum of all vector elements */
 float sum_f(
     const float *vec,  /* i  : input vector                                    */
diff --git a/lib_com/tools.c b/lib_com/tools.c
index 10633883fd155f9d4045923f253d266f5a2cc1de..9dfa8b9f81bc999cb6770fafc2cba16d6303fd53 100644
--- a/lib_com/tools.c
+++ b/lib_com/tools.c
@@ -138,6 +138,7 @@ int16_t sum_s(
     return tmp;
 }
 
+#ifdef DEBUGGING
 /*! r: sum of all vector elements */
 int32_t sum_l(
     const int32_t *vec, /* i  : input vector                          */
@@ -156,6 +157,7 @@ int32_t sum_l(
     return tmpL;
 }
 
+#endif
 /*! r: sum of all vector elements */
 float sum_f(
     const float *vec,  /* i  : input vector                          */