diff --git a/src/H5Dscatgath.c b/src/H5Dscatgath.c
index 8e456ba7d5e..30e91026330 100644
--- a/src/H5Dscatgath.c
+++ b/src/H5Dscatgath.c
@@ -541,6 +541,8 @@ H5D__scatgath_read(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_
                 (size_t)MIN(dset_info->type_info.request_nelmts, (dset_info->nelmts - smine_start));
         }
 
+memset(tmp_buf, 0, smine_nelmts * MAX(dset_info->type_info.src_type_size, dset_info->type_info.dst_type_size));
+
         /*
          * Gather the data from disk into the datatype conversion
          * buffer. Also gather data from application to background buffer
diff --git a/test/cmpd_dset.c b/test/cmpd_dset.c
index 97b296e68b0..6fd67d05d58 100644
--- a/test/cmpd_dset.c
+++ b/test/cmpd_dset.c
@@ -846,7 +846,7 @@ test_compounds_selection_io(void)
     for (set_cache = FALSE; set_cache <= FALSE; set_cache++) {
         for (set_fillvalue = FALSE; set_fillvalue <= FALSE; set_fillvalue++) {
             for (select_io = FALSE; select_io <= FALSE; select_io++) {
-                for (mwbuf = FALSE; mwbuf <= TRUE; mwbuf++) {
+                for (mwbuf = TRUE; mwbuf <= TRUE; mwbuf++) {
                     for (set_buf = FALSE; set_buf <= FALSE; set_buf++) {
 
                         if ((dxpl = H5Pcreate(H5P_DATASET_XFER)) < 0)