diff --git a/.github/workflows/clang.yml b/.github/workflows/clang.yml
index 939d5b98..1a278584 100644
--- a/.github/workflows/clang.yml
+++ b/.github/workflows/clang.yml
@@ -12,7 +12,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [macos-10.15]
+        os: [macos-11]
 
     steps:
     - uses: actions/checkout@v2
diff --git a/include/etl/platform.h b/include/etl/platform.h
index 770090d1..6c21e285 100644
--- a/include/etl/platform.h
+++ b/include/etl/platform.h
@@ -31,6 +31,7 @@ SOFTWARE.
 #ifndef ETL_PLATFORM_INCLUDED
 #define ETL_PLATFORM_INCLUDED
 
+#include <stddef.h>
 #include <stdint.h>
 #include <limits.h>