diff --git a/src/H5Dscatgath.c b/src/H5Dscatgath.c
index ff42b3646ee..295277df2b6 100644
--- a/src/H5Dscatgath.c
+++ b/src/H5Dscatgath.c
@@ -541,12 +541,6 @@ 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));
         }
 
-        if (H5D__SCATGATH_USE_CMPD_OPT_READ(dset_info, in_place_tconv)) {
-            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
@@ -560,7 +554,8 @@ H5D__scatgath_read(const H5D_io_info_t *io_info, const H5D_dset_io_info_t *dset_
             n = H5D__gather_mem(buf, bkg_iter, smine_nelmts, io_info->bkg_buf /*out*/);
             if (n != smine_nelmts)
                 HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "mem gather failed");
-        }
+        } else
+memset(tmp_buf, 0, smine_nelmts * MAX(dset_info->type_info.src_type_size, dset_info->type_info.dst_type_size));
 
         /*
          * Gather data
diff --git a/test/cmpd_dset.c b/test/cmpd_dset.c
index 6fd67d05d58..aff2ec5480e 100644
--- a/test/cmpd_dset.c
+++ b/test/cmpd_dset.c
@@ -343,13 +343,13 @@ test_select_src_subset(char *fname, hid_t fapl, hid_t in_dxpl, unsigned set_fill
         goto error;
 
     /* Allocate space and initialize data */
-    rbuf = (unsigned char *)malloc(NX * NY * sizeof(stype3));
+    rbuf = (unsigned char *)calloc(NX * NY, sizeof(stype3));
 
-    rew_buf = (unsigned char *)malloc(NX * NY * sizeof(stype3));
+    rew_buf = (unsigned char *)calloc(NX * NY, sizeof(stype3));
     initialize_stype3(rew_buf, (size_t)NX * NY);
 
     /* Save a copy as the buffer may be clobbered due to H5Pset_modify_write_buf() */
-    save_rew_buf = (unsigned char *)malloc(NX * NY * sizeof(stype3));
+    save_rew_buf = (unsigned char *)calloc(NX * NY, sizeof(stype3));
     initialize_stype3(save_rew_buf, (size_t)NX * NY);
 
     /* Create dataset creation property list */
@@ -639,15 +639,15 @@ test_select_compound(char *fname, hid_t fapl, hid_t in_dxpl, unsigned set_fillva
     hsize_t        memb_size[1] = {4};
 
     /* Allocate buffers */
-    if (NULL == (s1 = (s1_t *)malloc(sizeof(s1_t) * NX * NY)))
+    if (NULL == (s1 = (s1_t *)calloc(NX * NY, sizeof(s1_t))))
         goto error;
-    if (NULL == (rbuf1 = (s1_t *)malloc(sizeof(s1_t) * NX * NY)))
+    if (NULL == (rbuf1 = (s1_t *)calloc(NX * NY, sizeof(s1_t))))
         goto error;
-    if (NULL == (s3 = (s3_t *)malloc(sizeof(s3_t) * NX * NY)))
+    if (NULL == (s3 = (s3_t *)calloc(NX * NY, sizeof(s3_t))))
         goto error;
-    if (NULL == (save_s3 = (s3_t *)malloc(sizeof(s3_t) * NX * NY)))
+    if (NULL == (save_s3 = (s3_t *)calloc(NX * NY, sizeof(s3_t))))
         goto error;
-    if (NULL == (rbuf3 = (s3_t *)malloc(sizeof(s3_t) * NX * NY)))
+    if (NULL == (rbuf3 = (s3_t *)calloc(NX * NY, sizeof(s3_t))))
         goto error;
 
     /* Create the file */