diff --git a/pkgs/by-name/op/openmpi/package.nix b/pkgs/by-name/op/openmpi/package.nix
index 761b0e00c453..d3ef5d0fcad1 100644
--- a/pkgs/by-name/op/openmpi/package.nix
+++ b/pkgs/by-name/op/openmpi/package.nix
@@ -101,6 +101,8 @@ stdenv.mkDerivation (finalAttrs: {
     libnl
     numactl
     pmix
+  ]
+  ++ lib.optionals (lib.meta.availableOn stdenv.hostPlatform ucx) [
     ucx
     ucc
   ]
@@ -153,8 +155,10 @@ stdenv.mkDerivation (finalAttrs: {
         p = [
           "mpi"
         ]
-        ++ lib.optionals stdenv.hostPlatform.isLinux [
+        ++ lib.optionals (lib.meta.availableOn stdenv.hostPlatform ucx) [
           "shmem"
+        ]
+        ++ lib.optionals stdenv.hostPlatform.isLinux [
           "osh"
         ];
         s = [
@@ -201,7 +205,7 @@ stdenv.mkDerivation (finalAttrs: {
         part1 = [
           "mpi"
         ]
-        ++ lib.optionals stdenv.hostPlatform.isLinux [ "shmem" ];
+        ++ lib.optionals (lib.meta.availableOn stdenv.hostPlatform ucx) [ "shmem" ];
         part2 = builtins.attrNames wrapperDataSubstitutions;
       };
     in
diff --git a/pkgs/by-name/uc/ucx/package.nix b/pkgs/by-name/uc/ucx/package.nix
index a2df302dd232..c82c686ac243 100644
--- a/pkgs/by-name/uc/ucx/package.nix
+++ b/pkgs/by-name/uc/ucx/package.nix
@@ -36,14 +36,14 @@ let
   # rocm build fails with gcc stdenv due to unrecognised arg parallel-jobs
   stdenv' = if enableRocm then rocmPackages.stdenv else stdenv;
 in
-stdenv'.mkDerivation rec {
+stdenv'.mkDerivation (finalAttrs: {
   pname = "ucx";
   version = "1.18.1";
 
   src = fetchFromGitHub {
     owner = "openucx";
     repo = "ucx";
-    rev = "v${version}";
+    rev = "v${finalAttrs.version}";
     sha256 = "sha256-LW57wbQFwW14Z86p9jo1ervkCafVy+pnIQQ9t0i8enY=";
   };
 
@@ -103,11 +103,14 @@ stdenv'.mkDerivation rec {
 
   enableParallelBuilding = true;
 
-  meta = with lib; {
+  meta = {
     description = "Unified Communication X library";
     homepage = "https://www.openucx.org";
-    license = licenses.bsd3;
-    platforms = platforms.linux;
-    maintainers = [ maintainers.markuskowa ];
+    license = lib.licenses.bsd3;
+    platforms = lib.platforms.linux;
+    # LoongArch64 is not supported.
+    # See: https://github.com/openucx/ucx/issues/9873
+    badPlatforms = lib.platforms.loongarch64;
+    maintainers = with lib.maintainers; [ markuskowa ];
   };
-}
+})