diff --git a/ompi/mca/coll/libnbc/coll_libnbc_component.c b/ompi/mca/coll/libnbc/coll_libnbc_component.c
index 226507c564..bf4960d923 100644
--- a/ompi/mca/coll/libnbc/coll_libnbc_component.c
+++ b/ompi/mca/coll/libnbc/coll_libnbc_component.c
@@ -388,7 +388,8 @@ OBJ_CLASS_INSTANCE(ompi_coll_libnbc_module_t,
 static int
 request_start(size_t count, ompi_request_t ** requests)
 {
-    int i, res;
+    int res;
+    size_t i;
 
     NBC_DEBUG(5, " ** request_start **\n");
 
diff --git a/ompi/mca/coll/libnbc/nbc_ialltoallv.c b/ompi/mca/coll/libnbc/nbc_ialltoallv.c
index 2c433d0611..93f54aa20f 100644
--- a/ompi/mca/coll/libnbc/nbc_ialltoallv.c
+++ b/ompi/mca/coll/libnbc/nbc_ialltoallv.c
@@ -50,7 +50,7 @@ static int nbc_alltoallv_init(const void* sendbuf, const int *sendcounts, const
   MPI_Aint sndext, rcvext;
   NBC_Schedule *schedule;
   char *rbuf, *sbuf, inplace;
-  ptrdiff_t gap, span;
+  ptrdiff_t gap = 0, span;
   void * tmpbuf = NULL;
   ompi_coll_libnbc_module_t *libnbc_module = (ompi_coll_libnbc_module_t*) module;
 
diff --git a/ompi/mca/coll/libnbc/nbc_ialltoallw.c b/ompi/mca/coll/libnbc/nbc_ialltoallw.c
index 366c0aa752..52d53b121e 100644
--- a/ompi/mca/coll/libnbc/nbc_ialltoallw.c
+++ b/ompi/mca/coll/libnbc/nbc_ialltoallw.c
@@ -294,7 +294,7 @@ static inline int a2aw_sched_pairwise(int rank, int p, NBC_Schedule *schedule,
 static inline int a2aw_sched_inplace(int rank, int p, NBC_Schedule *schedule,
                                      void *buf, const int *counts, const int *displs,
                                      struct ompi_datatype_t * const * types) {
-  ptrdiff_t gap;
+  ptrdiff_t gap = 0;
   int res;
 
   for (int i = 1; i < (p+1)/2; i++) {