diff --git a/compiler-rt/lib/dfsan/dfsan_flags.inc b/compiler-rt/lib/dfsan/dfsan_flags.inc
--- a/compiler-rt/lib/dfsan/dfsan_flags.inc
+++ b/compiler-rt/lib/dfsan/dfsan_flags.inc
@@ -16,7 +16,7 @@
 // DFSAN_FLAG(Type, Name, DefaultValue, Description)
 // See COMMON_FLAG in sanitizer_flags.inc for more details.
 
-DFSAN_FLAG(bool, warn_unimplemented, true,
+DFSAN_FLAG(bool, warn_unimplemented, false,
            "Whether to warn on unimplemented functions.")
 DFSAN_FLAG(bool, warn_nonzero_labels, false,
            "Whether to warn on unimplemented functions.")
diff --git a/compiler-rt/test/dfsan/flags.c b/compiler-rt/test/dfsan/flags.c
--- a/compiler-rt/test/dfsan/flags.c
+++ b/compiler-rt/test/dfsan/flags.c
@@ -1,4 +1,4 @@
-// RUN: %clang_dfsan %s -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -mllvm -dfsan-debug-nonzero-labels -o %t && %run %t 2>&1 | FileCheck %s
+// RUN: %clang_dfsan %s -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -mllvm -dfsan-debug-nonzero-labels -o %t && DFSAN_OPTIONS=warn_unimplemented=1 %run %t 2>&1 | FileCheck %s
 // RUN: %clang_dfsan %s -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -mllvm -dfsan-debug-nonzero-labels -o %t && DFSAN_OPTIONS=warn_unimplemented=0 %run %t 2>&1 | count 0
 // RUN: %clang_dfsan %s -fsanitize-ignorelist=%S/Inputs/flags_abilist.txt -mllvm -dfsan-debug-nonzero-labels -o %t && DFSAN_OPTIONS=warn_nonzero_labels=1 %run %t 2>&1 | FileCheck --check-prefix=CHECK-NONZERO %s
 //