diff --git a/recipe/meta.yaml b/recipe/meta.yaml
index d1c44ba2..093bdec4 100644
--- a/recipe/meta.yaml
+++ b/recipe/meta.yaml
@@ -1,6 +1,6 @@
 {% set version = "11.0.0" %}
 {% set major_version = version.split(".")[0] %}
-{% set build_number = 1 %}
+{% set build_number = 2 %}
 
 package:
   name: clang_packages
@@ -16,6 +16,9 @@ source:
       - patches/0003-clang-Fix-normalizeProgramName-s-handling-of-dots-ou.patch
       - patches/0001-Set-VERSION-in-osx-as-well.patch
       - patches/cross-compile.diff
+      # Disable -Werror,-Wundef-prefix=TARGET_OS as they are not yet defined in the 10.9 SDK used for osx-64
+      # Only enable it for TARGET_OS_OSX.
+      - patches/disable-wundef-prefix.patch  # [osx and x86_64]
       #- patches/amd-roc-2.7.0.diff   # [variant != "hcc"]
       #- patches/amd-roc-hcc-2.7.0.diff  # [variant == "hcc"]
     folder: .
diff --git a/recipe/patches/disable-wundef-prefix.patch b/recipe/patches/disable-wundef-prefix.patch
new file mode 100644
index 00000000..68859a67
--- /dev/null
+++ b/recipe/patches/disable-wundef-prefix.patch
@@ -0,0 +1,11 @@
+--- lib/Driver/ToolChains/Darwin.cpp.orig	2020-11-17 21:12:24.000000000 +0100
++++ lib/Driver/ToolChains/Darwin.cpp	2020-11-17 21:12:37.000000000 +0100
+@@ -960,7 +960,7 @@
+ 
+ void DarwinClang::addClangWarningOptions(ArgStringList &CC1Args) const {
+   // Always error about undefined 'TARGET_OS_*' macros.
+-  CC1Args.push_back("-Wundef-prefix=TARGET_OS_");
++  CC1Args.push_back("-Wundef-prefix=TARGET_OS_OSX");
+   CC1Args.push_back("-Werror=undef-prefix");
+ 
+   // For modern targets, promote certain warnings to errors.