diff --git a/clang.spec b/clang.spec
index e99b5bc..98b825b 100644
--- a/clang.spec
+++ b/clang.spec
@@ -87,6 +87,7 @@ Source4:	tstellar-gpg-key.asc
 
 
 %if !0%{?compat_build}
+Patch21:	completion-model-cmake.patch
 Patch22:	clang-tidy.patch
 %endif
 
diff --git a/completion-model-cmake.patch b/completion-model-cmake.patch
new file mode 100644
index 0000000..925294d
--- /dev/null
+++ b/completion-model-cmake.patch
@@ -0,0 +1,14 @@
+diff -Naur clang-tools-extra-12.0.0rc1.src.orig/clangd/quality/CompletionModel.cmake clang-tools-extra-12.0.0rc1.src/clangd/quality/CompletionModel.cmake
+--- clang-tools-extra-12.0.0rc1.src.orig/clangd/quality/CompletionModel.cmake	2021-02-14 17:03:14.000000000 +0100
++++ clang-tools-extra-12.0.0rc1.src/clangd/quality/CompletionModel.cmake	2021-02-14 20:57:51.000000000 +0100
+@@ -5,8 +5,8 @@
+ # will define a C++ class called ${cpp_class} - which may be a
+ # namespace-qualified class name.
+ function(gen_decision_forest model filename cpp_class)
+-  set(model_compiler ${CMAKE_SOURCE_DIR}/../clang-tools-extra/clangd/quality/CompletionModelCodegen.py)
+-  
++  set(model_compiler ${LLVM_EXTERNAL_CLANG_TOOLS_EXTRA_SOURCE_DIR}/clangd/quality/CompletionModelCodegen.py)
++
+   set(output_dir ${CMAKE_CURRENT_BINARY_DIR})
+   set(header_file ${output_dir}/${filename}.h)
+   set(cpp_file ${output_dir}/${filename}.cpp)