diff --git a/ompi/mca/pml/ucx/pml_ucx.c b/ompi/mca/pml/ucx/pml_ucx.c
index 2a3a616f7c..26700ef075 100644
--- a/ompi/mca/pml/ucx/pml_ucx.c
+++ b/ompi/mca/pml/ucx/pml_ucx.c
@@ -68,8 +68,8 @@ mca_pml_ucx_module_t ompi_pml_ucx = {
         mca_pml_ucx_mrecv,
         mca_pml_ucx_dump,
         NULL, /* FT */
-        1ul << (PML_UCX_TAG_BITS - 1),
         1ul << (PML_UCX_CONTEXT_BITS),
+        1ul << (PML_UCX_TAG_BITS - 1),
     },
     NULL,   /* ucp_context */
     NULL    /* ucp_worker */
diff --git a/ompi/mca/pml/ucx/pml_ucx_request.h b/ompi/mca/pml/ucx/pml_ucx_request.h
index 616ec84d79..482e1a539a 100644
--- a/ompi/mca/pml/ucx/pml_ucx_request.h
+++ b/ompi/mca/pml/ucx/pml_ucx_request.h
@@ -26,15 +26,15 @@ enum {
 /*
  * UCX tag structure:
  *
- * 01234567 01234567 01234567 01234567 01234567 01234567 01234567 01234567
- *                           |                          |
- *      message tag (24)     |     source rank (24)     |  context id (16)
- *                           |                          |
+ * 01234567 01234567 01234567 01234567 01234567 0123 4567 01234567 01234567
+ *                           |                      |
+ *      message tag (24)     |   source rank (20)   |     context id (20)
+ *                           |                      |
  */
 #define PML_UCX_TAG_BITS                       24
-#define PML_UCX_RANK_BITS                      24
-#define PML_UCX_CONTEXT_BITS                   16
-#define PML_UCX_ANY_SOURCE_MASK                0x800000000000fffful
+#define PML_UCX_RANK_BITS                      20
+#define PML_UCX_CONTEXT_BITS                   20
+#define PML_UCX_ANY_SOURCE_MASK                0x80000000000ffffful
 #define PML_UCX_SPECIFIC_SOURCE_MASK           0x800000fffffffffful
 #define PML_UCX_TAG_MASK                       0x7fffff0000000000ul