diff --git a/pkgs/development/compilers/llvm/3.9/clang/0001-Fix-compilation-w-gcc9.patch b/pkgs/development/compilers/llvm/3.9/clang/0001-Fix-compilation-w-gcc9.patch
new file mode 100644
index 000000000000..1058cd031767
--- /dev/null
+++ b/pkgs/development/compilers/llvm/3.9/clang/0001-Fix-compilation-w-gcc9.patch
@@ -0,0 +1,63 @@
+From 7225c7754cc3431d05df367c60f309f27586f188 Mon Sep 17 00:00:00 2001
+From: Maximilian Bosch <maximilian@mbosch.me>
+Date: Mon, 30 Dec 2019 01:42:52 +0100
+Subject: [PATCH] Fix compilation w/gcc9
+
+Build broken with the following errors:
+
+```
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp: In lambda function:
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp:6078:55: error: lambda parameter 'CGF' previously declared as a capture
+clang> 6078 |                          &NumOfPtrs](CodeGenFunction &CGF, PrePostActionTy &) {
+clang> |                                      ~~~~~~~~~~~~~~~~~^~~
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp: In lambda function:
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp:6126:53: error: lambda parameter 'CGF' previously declared as a capture
+clang> 6126 |                        &NumOfPtrs](CodeGenFunction &CGF, PrePostActionTy &) {
+clang> |                                    ~~~~~~~~~~~~~~~~~^~~
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp: In lambda function:
+clang> /build/clang/lib/CodeGen/CGOpenMPRuntime.cpp:6191:56: error: lambda parameter 'CGF' previously declared as a capture
+clang> 6191 |   auto &&ThenGen = [&D, &CGF, Device](CodeGenFunction &CGF, PrePostActionTy &) {
+clang> |                                       ~~~~~~~~~~~~~~~~~^~~
+```
+
+This was due to a bug about name-collisions fixed in GCC 9.0[1].
+
+[1] http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2211
+---
+ lib/CodeGen/CGOpenMPRuntime.cpp | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/lib/CodeGen/CGOpenMPRuntime.cpp b/lib/CodeGen/CGOpenMPRuntime.cpp
+index 6a0edbe..96c281c 100644
+--- a/lib/CodeGen/CGOpenMPRuntime.cpp
++++ b/lib/CodeGen/CGOpenMPRuntime.cpp
+@@ -6073,7 +6073,7 @@ void CGOpenMPRuntime::emitTargetDataCalls(CodeGenFunction &CGF,
+   // Generate the code for the opening of the data environment. Capture all the
+   // arguments of the runtime call by reference because they are used in the
+   // closing of the region.
+-  auto &&BeginThenGen = [&D, &CGF, &BasePointersArray, &PointersArray,
++  auto &&BeginThenGen = [&D, &BasePointersArray, &PointersArray,
+                          &SizesArray, &MapTypesArray, Device,
+                          &NumOfPtrs](CodeGenFunction &CGF, PrePostActionTy &) {
+     // Fill up the arrays with all the mapped variables.
+@@ -6121,7 +6121,7 @@ void CGOpenMPRuntime::emitTargetDataCalls(CodeGenFunction &CGF,
+   };
+ 
+   // Generate code for the closing of the data region.
+-  auto &&EndThenGen = [&CGF, &BasePointersArray, &PointersArray, &SizesArray,
++  auto &&EndThenGen = [&BasePointersArray, &PointersArray, &SizesArray,
+                        &MapTypesArray, Device,
+                        &NumOfPtrs](CodeGenFunction &CGF, PrePostActionTy &) {
+     assert(BasePointersArray && PointersArray && SizesArray && MapTypesArray &&
+@@ -6188,7 +6188,7 @@ void CGOpenMPRuntime::emitTargetDataStandAloneCall(
+          "Expecting either target enter, exit data, or update directives.");
+ 
+   // Generate the code for the opening of the data environment.
+-  auto &&ThenGen = [&D, &CGF, Device](CodeGenFunction &CGF, PrePostActionTy &) {
++  auto &&ThenGen = [&D, Device](CodeGenFunction &CGF, PrePostActionTy &) {
+     // Fill up the arrays with all the mapped variables.
+     MappableExprsHandler::MapValuesArrayTy BasePointers;
+     MappableExprsHandler::MapValuesArrayTy Pointers;
+-- 
+2.23.1
+
diff --git a/pkgs/development/compilers/llvm/3.9/clang/default.nix b/pkgs/development/compilers/llvm/3.9/clang/default.nix
index 3d09277ad4cf..1666b3d842d9 100644
--- a/pkgs/development/compilers/llvm/3.9/clang/default.nix
+++ b/pkgs/development/compilers/llvm/3.9/clang/default.nix
@@ -27,7 +27,10 @@ let
     (stdenv.lib.optional stdenv.isLinux "-DGCC_INSTALL_PREFIX=${gcc}") ++
     (stdenv.lib.optional (stdenv.cc.libc != null) "-DC_INCLUDE_DIRS=${stdenv.cc.libc}/include");
 
-    patches = [ ./purity.patch ];
+    patches = [
+      ./purity.patch
+      ./0001-Fix-compilation-w-gcc9.patch
+    ];
 
     postPatch = ''
       sed -i -e 's/Args.hasArg(options::OPT_nostdlibinc)/true/' lib/Driver/Tools.cpp