diff --git a/pkgs/intel-oneapi/packages.nix b/pkgs/intel-oneapi/packages.nix
index 69653886..aa8cab35 100644
--- a/pkgs/intel-oneapi/packages.nix
+++ b/pkgs/intel-oneapi/packages.nix
@@ -233,6 +233,8 @@ let
       mkl = "2025.2";
       mpi = "2021.16";
       tbb = "2022.2";
+
+      llvmMajorVersion = 21;
     };
     "2024" = {
       tcm = "1.1";
@@ -252,6 +254,8 @@ let
       mpi = "2021.13";
       tbb = "2021.13";
 
+      llvmMajorVersion = 19;
+
       extraPackages = [
         sqlite
         elfutils
diff --git a/pkgs/intel-oneapi/patch_intel.nix b/pkgs/intel-oneapi/patch_intel.nix
index cfe7d86d..56a74b30 100644
--- a/pkgs/intel-oneapi/patch_intel.nix
+++ b/pkgs/intel-oneapi/patch_intel.nix
@@ -39,7 +39,9 @@ lib.makeOverridable (
       removeAttrs
       ;
 
-    __components = removeAttrs components [ "extraPackages" ];
+    inherit (components) llvmMajorVersion;
+
+    __components = removeAttrs components [ "extraPackages" "llvmMajorVersion" ];
     _components = __components;
     # _components = lib.traceSeqN 2 {
     #   inherit unpatched __components;
@@ -63,7 +65,7 @@ lib.makeOverridable (
           ];
           cc-cflags = [
             "--gcc-toolchain=${gcc.cc}"
-            "-isystem \"${cc.original}/lib/clang/*/include\""
+            "-isystem ${cc.original or cc}/lib/clang/${toString cc.llvmMajorVersion}/include"
             "-isystem ${cc}/include"
             "-isystem ${cc}/include/intel64"
             "-isystem ${gcc.cc}/lib/gcc/${targetConfig}/${gcc.version}/include"
@@ -171,7 +173,7 @@ lib.makeOverridable (
             pname = "intel-${folder}";
             inherit version;
             paths = [ original ] ++ lib.optionals (folder == "compiler") [ etc-vendors ];
-            passthru = { inherit original; };
+            passthru = { inherit original llvmMajorVersion; };
           }
         ) _components;
       in