diff --git a/Makefile b/Makefile
index 26a5d7e4ec5c603c11b4bdee602069515bdf58db..8ccf3a15c519732c160d17afc49d7e7fcdc8bc9e 100644
--- a/Makefile
+++ b/Makefile
@@ -143,7 +143,7 @@ CC_tsan = clang
 CXX_tsan = clang++
 LD_tsan = clang
 LDXX_tsan = clang++
-CPPFLAGS_tsan = -O1 -fsanitize=thread -fno-omit-frame-pointer
+CPPFLAGS_tsan = -O0 -fsanitize=thread -fno-omit-frame-pointer
 LDFLAGS_tsan = -fsanitize=thread
 DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10
 
diff --git a/templates/Makefile.template b/templates/Makefile.template
index bc8f1bb1d071b7db97b864ae18bf0bded5a5acb0..099a722873c6a988ecc102dcf126069fcd9510a8 100644
--- a/templates/Makefile.template
+++ b/templates/Makefile.template
@@ -157,7 +157,7 @@ CC_tsan = clang
 CXX_tsan = clang++
 LD_tsan = clang
 LDXX_tsan = clang++
-CPPFLAGS_tsan = -O1 -fsanitize=thread -fno-omit-frame-pointer
+CPPFLAGS_tsan = -O0 -fsanitize=thread -fno-omit-frame-pointer
 LDFLAGS_tsan = -fsanitize=thread
 DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10