diff --git a/packages/o/openmp/xmake.lua b/packages/o/openmp/xmake.lua
index 0b7260d50..af379e1d7 100644
--- a/packages/o/openmp/xmake.lua
+++ b/packages/o/openmp/xmake.lua
@@ -7,62 +7,68 @@ package("openmp")
     add_configs("experimental", {description = "Enable experimental OpenMP feature for msvc.", default = true, type = boolean})
 
     on_load(function (package)
+        if package.has_tool then
+            for _, toolkind in ipairs({"cc", "cxx"}) do
+                if package:config("runtime") == "default" then
+                    if package:has_tool(toolkind, "clang", "clangxx") then
+                        if package:is_plat("macosx") then
+                            package:add("deps", "libomp") -- need to tell apple clang from llvm clang
+                        end
+                    end
+                end
+            end
+        end
+    end)
+
+    on_fetch(function (package)
+        for _, dep in ipairs(package:orderdeps()) do
+            if not dep:fetch() then
+                return
+            end
+        end
+        local result = {}
         if package.has_tool then
             for _, toolkind in ipairs({"cc", "cxx"}) do
                 local flagname = toolkind == "cxx" and "cxxflags" or "cflags"
                 if package:has_tool(toolkind, "cl") then
-                    package:add(flagname, (package:config("experimental") and "/openmp:experimental" or "/openmp"))
+                    result[flagname] = (package:config("experimental") and "/openmp:experimental" or "/openmp")
                 elseif package:has_tool(toolkind, "clang", "clangxx") then
                     if package:is_plat("macosx") then
-                        package:add(flagname, "-Xpreprocessor -fopenmp")
+                        result[flagname] = "-Xpreprocessor -fopenmp"
                     else
-                        package:add(flagname, "-fopenmp")
+                        result[flagname] = "-fopenmp"
                     end
                 elseif package:has_tool(toolkind, "gcc", "gxx") then
-                    package:add(flagname, "-fopenmp")
+                    result[flagname] = "-fopenmp"
                 elseif package:has_tool(toolkind, "icc", "icpc") then
-                    package:add(flagname, "-qopenmp")
+                    result[flagname] = "-qopenmp"
                 elseif package:has_tool(toolkind, "icl") then
-                    package:add(flagname, "-Qopenmp")
+                    result[flagname] = "-Qopenmp"
                 end
                 if package:config("runtime") == "default" then
                     if package:has_tool(toolkind, "cl") then
-                        package:add("ldflags", "/openmp")
+                        result.ldflags = "/openmp"
                     elseif package:has_tool(toolkind, "clang", "clangxx") then
-                        if package:is_plat("macosx") then
-                            package:add("deps", "libomp") -- need to tell apple clang from llvm clang
-                        else
-                            package:add("ldflags", "-fopenmp")
+                        if not package:is_plat("macosx") then
+                            result.ldflags = "-fopenmp"
                         end
                     elseif package:has_tool(toolkind, "gcc", "gxx") then
-                        package:add("ldflags", "-fopenmp")
+                        result.ldflags = "-fopenmp"
                     elseif package:has_tool(toolkind, "icc", "icpc") then
-                        package:add("ldflags", "-qopenmp")
+                        result.ldflags = "-qopenmp"
                     elseif package:has_tool(toolkind, "icl") then
-                        package:add("ldflags", "-Qopenmp")
+                        result.ldflags = "-Qopenmp"
                     end
                 end
                 if package:config("runtime") == "custom" then
                     if package:has_tool(toolkind, "cl") then
-                        package:add("ldflags", "/openmp")
-                        package:add("ldflags", "/nodefaultlib:vcomp")
+                        result.ldflags = "/openmp"
+                        result.ldflags = "/nodefaultlib:vcomp"
                     end
                 end
             end
         end
-    end)
-
-    on_fetch(function (package)
-        for _, dep in ipairs(package:orderdeps()) do
-            if not dep:fetch() then
-                return
-            end
-        end
-        -- we need fetch the installed flags in on_load
-        local manifest = package:manifest_load()
-        if manifest then
-            return manifest.vars
-        end
+        return (result.cflags or result.cxxflags) and result
     end)
 
     on_install("linux", "macosx", "windows", function (package)