diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9893a8361..962c2afbc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -262,6 +262,7 @@ add_library(stdexec_executable_flags INTERFACE)
 
 # Enable warnings
 target_compile_options(stdexec_executable_flags INTERFACE
+                       $<$<CXX_COMPILER_ID:Clang>:-pedantic-errors;-Wall;-Wextra;-Werror>
                        $<$<STREQUAL:${stdexec_compiler_frontend},GNU>:-Wall;-Werror=unused-parameter>
                        $<$<STREQUAL:${stdexec_compiler_frontend},AppleClang>:-Wall>
                        $<$<STREQUAL:${stdexec_compiler_frontend},MSVC>:/W4>)
diff --git a/include/stdexec/__detail/__read_env.hpp b/include/stdexec/__detail/__read_env.hpp
index b36e8dfd1..637317c64 100644
--- a/include/stdexec/__detail/__read_env.hpp
+++ b/include/stdexec/__detail/__read_env.hpp
@@ -57,7 +57,7 @@ namespace STDEXEC
       }
 
       _Receiver       __rcvr_;
-      __optional<_Ty> __result_;
+      __optional<_Ty> __result_ = __nullopt;
     };
 
     template <class _Receiver, class _Query, class _Ty>