diff --git a/ompi/mca/coll/ucc/coll_ucc_allgather.c b/ompi/mca/coll/ucc/coll_ucc_allgather.c
index 3312d818bf3..2dd3ac68a55 100644
--- a/ompi/mca/coll/ucc/coll_ucc_allgather.c
+++ b/ompi/mca/coll/ucc/coll_ucc_allgather.c
@@ -15,15 +15,20 @@ static inline ucc_status_t mca_coll_ucc_allgather_init(const void *sbuf, size_t
                                                        ucc_coll_req_h *req,
                                                        mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t         ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
     int comm_size = ompi_comm_size(ucc_module->comm);
 
-    if (!ompi_datatype_is_contiguous_memory_layout(sdtype, scount) ||
+    if (!(is_inplace || ompi_datatype_is_contiguous_memory_layout(sdtype, scount)) ||
         !ompi_datatype_is_contiguous_memory_layout(rdtype, rcount * comm_size)) {
         goto fallback;
     }
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+
     ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+    if (!is_inplace) {
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+    }
+
     if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt ||
         COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
         UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
@@ -50,7 +55,7 @@ static inline ucc_status_t mca_coll_ucc_allgather_init(const void *sbuf, size_t
         }
     };
 
-    if (MPI_IN_PLACE == sbuf) {
+    if (is_inplace) {
         coll.mask  = UCC_COLL_ARGS_FIELD_FLAGS;
         coll.flags = UCC_COLL_ARGS_FLAG_IN_PLACE;
     }
diff --git a/ompi/mca/coll/ucc/coll_ucc_allgatherv.c b/ompi/mca/coll/ucc/coll_ucc_allgatherv.c
index 3190eceb857..68e786e0c2a 100644
--- a/ompi/mca/coll/ucc/coll_ucc_allgatherv.c
+++ b/ompi/mca/coll/ucc/coll_ucc_allgatherv.c
@@ -9,7 +9,7 @@
 
 #include "coll_ucc_common.h"
 
-static inline ucc_status_t mca_coll_ucc_allgatherv_init(const void *sbuf, int scount,
+static inline ucc_status_t mca_coll_ucc_allgatherv_init(const void *sbuf, size_t scount,
                                                         struct ompi_datatype_t *sdtype,
                                                         void* rbuf, ompi_count_array_t rcounts, ompi_disp_array_t rdisps,
                                                         struct ompi_datatype_t *rdtype,
@@ -17,10 +17,15 @@ static inline ucc_status_t mca_coll_ucc_allgatherv_init(const void *sbuf, int sc
                                                         ucc_coll_req_h *req,
                                                         mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t         ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
+    uint64_t flags = 0;
 
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
     ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+    if (!is_inplace) {
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+    }
+
     if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt ||
         COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
         UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
@@ -29,13 +34,13 @@ static inline ucc_status_t mca_coll_ucc_allgatherv_init(const void *sbuf, int sc
         goto fallback;
     }
 
-    uint64_t flags = ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0;
-    flags |= ompi_disp_array_is_64bit(rdisps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0;
+    flags = (ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0) |
+            (ompi_disp_array_is_64bit(rdisps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0) |
+            (is_inplace ? UCC_COLL_ARGS_FLAG_IN_PLACE : 0);
 
     ucc_coll_args_t coll = {
+        .mask      = flags ? UCC_COLL_ARGS_FIELD_FLAGS : 0,
         .flags     = flags,
-        .mask      = 0,
-        .flags     = 0,
         .coll_type = UCC_COLL_TYPE_ALLGATHERV,
         .src.info = {
             .buffer        = (void*)sbuf,
@@ -52,10 +57,6 @@ static inline ucc_status_t mca_coll_ucc_allgatherv_init(const void *sbuf, int sc
         }
     };
 
-    if (MPI_IN_PLACE == sbuf) {
-        coll.mask  = UCC_COLL_ARGS_FIELD_FLAGS;
-        coll.flags |= UCC_COLL_ARGS_FLAG_IN_PLACE;
-    }
     COLL_UCC_REQ_INIT(coll_req, req, coll, ucc_module);
     return UCC_OK;
 fallback:
diff --git a/ompi/mca/coll/ucc/coll_ucc_alltoall.c b/ompi/mca/coll/ucc/coll_ucc_alltoall.c
index 275f8d67640..cfb56f47418 100644
--- a/ompi/mca/coll/ucc/coll_ucc_alltoall.c
+++ b/ompi/mca/coll/ucc/coll_ucc_alltoall.c
@@ -15,15 +15,20 @@ static inline ucc_status_t mca_coll_ucc_alltoall_init(const void *sbuf, size_t s
                                                       ucc_coll_req_h *req,
                                                       mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t         ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
     int comm_size = ompi_comm_size(ucc_module->comm);
 
-    if (!ompi_datatype_is_contiguous_memory_layout(sdtype, scount * comm_size) ||
+    if (!(is_inplace || ompi_datatype_is_contiguous_memory_layout(sdtype, scount * comm_size)) ||
         !ompi_datatype_is_contiguous_memory_layout(rdtype, rcount * comm_size)) {
         goto fallback;
     }
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+
     ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+    if (!is_inplace) {
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+    }
+
     if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt ||
         COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
         UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
@@ -50,7 +55,7 @@ static inline ucc_status_t mca_coll_ucc_alltoall_init(const void *sbuf, size_t s
         }
     };
 
-    if (MPI_IN_PLACE == sbuf) {
+    if (is_inplace) {
         coll.mask  = UCC_COLL_ARGS_FIELD_FLAGS;
         coll.flags = UCC_COLL_ARGS_FLAG_IN_PLACE;
     }
diff --git a/ompi/mca/coll/ucc/coll_ucc_alltoallv.c b/ompi/mca/coll/ucc/coll_ucc_alltoallv.c
index 728636379b8..1e9e311cf94 100644
--- a/ompi/mca/coll/ucc/coll_ucc_alltoallv.c
+++ b/ompi/mca/coll/ucc/coll_ucc_alltoallv.c
@@ -17,10 +17,15 @@ static inline ucc_status_t mca_coll_ucc_alltoallv_init(const void *sbuf, ompi_co
                                                        ucc_coll_req_h *req,
                                                        mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t         ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
+    uint64_t flags = 0;
 
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
     ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+    if (!is_inplace) {
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+    }
+
     if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt ||
         COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
         UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
@@ -30,13 +35,13 @@ static inline ucc_status_t mca_coll_ucc_alltoallv_init(const void *sbuf, ompi_co
     }
 
     /* Assumes that send counts/displs and recv counts/displs are both 32-bit or both 64-bit */
-    uint64_t flags = ompi_count_array_is_64bit(scounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0;
-    flags |= ompi_disp_array_is_64bit(sdisps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0;
+    flags = (ompi_count_array_is_64bit(scounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0) |
+            (ompi_disp_array_is_64bit(sdisps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0) |
+            (is_inplace ? UCC_COLL_ARGS_FLAG_IN_PLACE : 0);
 
     ucc_coll_args_t coll = {
+        .mask      = flags ? UCC_COLL_ARGS_FIELD_FLAGS : 0,
         .flags     = flags,
-        .mask      = 0,
-        .flags     = 0,
         .coll_type = UCC_COLL_TYPE_ALLTOALLV,
         .src.info_v = {
             .buffer        = (void*)sbuf,
@@ -54,10 +59,6 @@ static inline ucc_status_t mca_coll_ucc_alltoallv_init(const void *sbuf, ompi_co
         }
     };
 
-    if (MPI_IN_PLACE == sbuf) {
-        coll.mask  = UCC_COLL_ARGS_FIELD_FLAGS;
-        coll.flags |= UCC_COLL_ARGS_FLAG_IN_PLACE;
-    }
     COLL_UCC_REQ_INIT(coll_req, req, coll, ucc_module);
     return UCC_OK;
 fallback:
diff --git a/ompi/mca/coll/ucc/coll_ucc_gather.c b/ompi/mca/coll/ucc/coll_ucc_gather.c
index 2b4b2e05474..ba91b40b189 100644
--- a/ompi/mca/coll/ucc/coll_ucc_gather.c
+++ b/ompi/mca/coll/ucc/coll_ucc_gather.c
@@ -17,27 +17,35 @@ ucc_status_t mca_coll_ucc_gather_init(const void *sbuf, size_t scount, struct om
                                       ucc_coll_req_h *req,
                                       mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
     int comm_rank = ompi_comm_rank(ucc_module->comm);
     int comm_size = ompi_comm_size(ucc_module->comm);
 
-    if (!ompi_datatype_is_contiguous_memory_layout(sdtype, scount)) {
-        goto fallback;
-    }
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
     if (comm_rank == root) {
-        if (!ompi_datatype_is_contiguous_memory_layout(rdtype, rcount * comm_size)) {
+        if (!(is_inplace || ompi_datatype_is_contiguous_memory_layout(sdtype, scount)) ||
+            !ompi_datatype_is_contiguous_memory_layout(rdtype, rcount * comm_size)) {
             goto fallback;
         }
+
         ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
-        if ((COLL_UCC_DT_UNSUPPORTED == ucc_rdt) ||
-            (MPI_IN_PLACE != sbuf && COLL_UCC_DT_UNSUPPORTED == ucc_sdt)) {
+        if (!is_inplace) {
+            ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+        }
+
+        if ((COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ||
+            (COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
-                        (COLL_UCC_DT_UNSUPPORTED == ucc_rdt) ?
-                        rdtype->super.name : sdtype->super.name);
+                        (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ?
+                        sdtype->super.name : rdtype->super.name);
             goto fallback;
         }
     } else {
+        if (!ompi_datatype_is_contiguous_memory_layout(sdtype, scount)) {
+            goto fallback;
+        }
+
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
         if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         sdtype->super.name);
@@ -64,7 +72,7 @@ ucc_status_t mca_coll_ucc_gather_init(const void *sbuf, size_t scount, struct om
         },
     };
 
-    if (MPI_IN_PLACE == sbuf) {
+    if (is_inplace) {
         coll.mask |= UCC_COLL_ARGS_FIELD_FLAGS;
         coll.flags = UCC_COLL_ARGS_FLAG_IN_PLACE;
     }
diff --git a/ompi/mca/coll/ucc/coll_ucc_gatherv.c b/ompi/mca/coll/ucc/coll_ucc_gatherv.c
index b53d69c9b76..5a1da52356c 100644
--- a/ompi/mca/coll/ucc/coll_ucc_gatherv.c
+++ b/ompi/mca/coll/ucc/coll_ucc_gatherv.c
@@ -17,20 +17,25 @@ static inline ucc_status_t mca_coll_ucc_gatherv_init(const void *sbuf, size_t sc
                                                      ucc_coll_req_h *req,
                                                      mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == sbuf);
     int comm_rank = ompi_comm_rank(ucc_module->comm);
+    uint64_t flags = 0;
 
-    ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
     if (comm_rank == root) {
         ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
-        if ((COLL_UCC_DT_UNSUPPORTED == ucc_rdt) ||
-            (MPI_IN_PLACE != sbuf && COLL_UCC_DT_UNSUPPORTED == ucc_sdt)) {
+        if (!is_inplace) {
+            ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+        }
+        if ((COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ||
+            (COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
-                        (COLL_UCC_DT_UNSUPPORTED == ucc_rdt) ?
-                        rdtype->super.name : sdtype->super.name);
+                        (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ?
+                        sdtype->super.name : rdtype->super.name);
             goto fallback;
         }
     } else {
+        ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
         if (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         sdtype->super.name);
@@ -38,13 +43,13 @@ static inline ucc_status_t mca_coll_ucc_gatherv_init(const void *sbuf, size_t sc
         }
     }
 
-    uint64_t flags = ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0;
-    flags |= ompi_disp_array_is_64bit(disps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0;
+    flags = (ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0) |
+            (ompi_disp_array_is_64bit(disps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0) |
+            (is_inplace ? UCC_COLL_ARGS_FLAG_IN_PLACE : 0);
 
     ucc_coll_args_t coll = {
+        .mask      = flags ? UCC_COLL_ARGS_FIELD_FLAGS : 0,
         .flags     = flags,
-        .mask      = 0,
-        .flags     = 0,
         .coll_type = UCC_COLL_TYPE_GATHERV,
         .root      = root,
         .src.info = {
@@ -62,10 +67,6 @@ static inline ucc_status_t mca_coll_ucc_gatherv_init(const void *sbuf, size_t sc
         },
     };
 
-    if (MPI_IN_PLACE == sbuf) {
-        coll.mask |= UCC_COLL_ARGS_FIELD_FLAGS;
-        coll.flags |= UCC_COLL_ARGS_FLAG_IN_PLACE;
-    }
     COLL_UCC_REQ_INIT(coll_req, req, coll, ucc_module);
     return UCC_OK;
 fallback:
diff --git a/ompi/mca/coll/ucc/coll_ucc_reduce_scatter.c b/ompi/mca/coll/ucc/coll_ucc_reduce_scatter.c
index 0df89160e8a..dabc8f11d03 100644
--- a/ompi/mca/coll/ucc/coll_ucc_reduce_scatter.c
+++ b/ompi/mca/coll/ucc/coll_ucc_reduce_scatter.c
@@ -21,6 +21,7 @@ ucc_status_t mca_coll_ucc_reduce_scatter_init(const void *sbuf, void *rbuf, ompi
     size_t total_count;
     int i;
     int comm_size = ompi_comm_size(ucc_module->comm);
+    uint64_t flags = 0;
 
     if (MPI_IN_PLACE == sbuf) {
         /* TODO: UCC defines inplace differently:
@@ -46,10 +47,11 @@ ucc_status_t mca_coll_ucc_reduce_scatter_init(const void *sbuf, void *rbuf, ompi
         total_count += ompi_count_array_get(rcounts, i);
     }
 
+    flags = (ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0);
+
     ucc_coll_args_t coll = {
-        .flags     = ompi_count_array_is_64bit(rcounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0,
-        .mask      = 0,
-        .flags     = 0,
+        .mask      = flags ? UCC_COLL_ARGS_FIELD_FLAGS : 0,
+        .flags     = flags,
         .coll_type = UCC_COLL_TYPE_REDUCE_SCATTERV,
         .src.info = {
             .buffer   = (void*)sbuf,
diff --git a/ompi/mca/coll/ucc/coll_ucc_scatter.c b/ompi/mca/coll/ucc/coll_ucc_scatter.c
index 55351b8151b..481365f22bd 100644
--- a/ompi/mca/coll/ucc/coll_ucc_scatter.c
+++ b/ompi/mca/coll/ucc/coll_ucc_scatter.c
@@ -18,21 +18,35 @@ ucc_status_t mca_coll_ucc_scatter_init(const void *sbuf, size_t scount,
                                        ucc_coll_req_h *req,
                                        mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == rbuf);
     int comm_rank = ompi_comm_rank(ucc_module->comm);
     int comm_size = ompi_comm_size(ucc_module->comm);
 
-    ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
     if (comm_rank == root) {
+        if (!(is_inplace || ompi_datatype_is_contiguous_memory_layout(rdtype, rcount)) ||
+            !ompi_datatype_is_contiguous_memory_layout(sdtype, scount * comm_size)) {
+            goto fallback;
+        }
+
         ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+        if (!is_inplace) {
+            ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+        }
+
         if ((COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ||
-            (MPI_IN_PLACE != rbuf && COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
+            (COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ?
                         sdtype->super.name : rdtype->super.name);
             goto fallback;
         }
     } else {
+        if (!ompi_datatype_is_contiguous_memory_layout(rdtype, rcount)) {
+            goto fallback;
+        }
+
+        ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
         if (COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         rdtype->super.name);
@@ -59,7 +73,7 @@ ucc_status_t mca_coll_ucc_scatter_init(const void *sbuf, size_t scount,
         },
     };
 
-    if (MPI_IN_PLACE == rbuf) {
+    if (is_inplace) {
         coll.mask |= UCC_COLL_ARGS_FIELD_FLAGS;
         coll.flags = UCC_COLL_ARGS_FLAG_IN_PLACE;
     }
diff --git a/ompi/mca/coll/ucc/coll_ucc_scatterv.c b/ompi/mca/coll/ucc/coll_ucc_scatterv.c
index 08d7dee60aa..36d4086a113 100644
--- a/ompi/mca/coll/ucc/coll_ucc_scatterv.c
+++ b/ompi/mca/coll/ucc/coll_ucc_scatterv.c
@@ -18,22 +18,25 @@ ucc_status_t mca_coll_ucc_scatterv_init(const void *sbuf, ompi_count_array_t sco
                                         ucc_coll_req_h *req,
                                         mca_coll_ucc_req_t *coll_req)
 {
-    ucc_datatype_t ucc_sdt, ucc_rdt;
+    ucc_datatype_t ucc_sdt = UCC_DT_INT8, ucc_rdt = UCC_DT_INT8;
+    bool is_inplace = (MPI_IN_PLACE == rbuf);
     int comm_rank = ompi_comm_rank(ucc_module->comm);
-    int comm_size = ompi_comm_size(ucc_module->comm);
-
-    ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+    uint64_t flags = 0;
     if (comm_rank == root) {
         ucc_sdt = ompi_dtype_to_ucc_dtype(sdtype);
+        if (!is_inplace) {
+            ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
+        }
+
         if ((COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ||
-            (MPI_IN_PLACE != rbuf && COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
+            (COLL_UCC_DT_UNSUPPORTED == ucc_rdt)) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         (COLL_UCC_DT_UNSUPPORTED == ucc_sdt) ?
                         sdtype->super.name : rdtype->super.name);
             goto fallback;
         }
-
     } else {
+        ucc_rdt = ompi_dtype_to_ucc_dtype(rdtype);
         if (COLL_UCC_DT_UNSUPPORTED == ucc_rdt) {
             UCC_VERBOSE(5, "ompi_datatype is not supported: dtype = %s",
                         rdtype->super.name);
@@ -41,13 +44,13 @@ ucc_status_t mca_coll_ucc_scatterv_init(const void *sbuf, ompi_count_array_t sco
         }
     }
 
-    uint64_t flags = ompi_count_array_is_64bit(scounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0;
-    flags |= ompi_disp_array_is_64bit(disps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0;
+    flags = (ompi_count_array_is_64bit(scounts) ? UCC_COLL_ARGS_FLAG_COUNT_64BIT : 0) |
+            (ompi_disp_array_is_64bit(disps) ? UCC_COLL_ARGS_FLAG_DISPLACEMENTS_64BIT : 0) |
+            (is_inplace ? UCC_COLL_ARGS_FLAG_IN_PLACE : 0);
 
     ucc_coll_args_t coll = {
+        .mask      = flags ? UCC_COLL_ARGS_FIELD_FLAGS : 0,
         .flags     = flags,
-        .mask      = 0,
-        .flags     = 0,
         .coll_type = UCC_COLL_TYPE_SCATTERV,
         .root      = root,
         .src.info_v = {
@@ -65,10 +68,6 @@ ucc_status_t mca_coll_ucc_scatterv_init(const void *sbuf, ompi_count_array_t sco
         },
     };
 
-    if (MPI_IN_PLACE == rbuf) {
-        coll.mask |= UCC_COLL_ARGS_FIELD_FLAGS;
-        coll.flags |= UCC_COLL_ARGS_FLAG_IN_PLACE;
-    }
     COLL_UCC_REQ_INIT(coll_req, req, coll, ucc_module);
     return UCC_OK;
 fallback: