diff --git a/bolt/test/X86/lit.local.cfg b/bolt/test/X86/lit.local.cfg
index 680ebdd1eb6b..ea9928d19188 100644
--- a/bolt/test/X86/lit.local.cfg
+++ b/bolt/test/X86/lit.local.cfg
@@ -1,7 +1,7 @@
 if not "X86" in config.root.targets:
     config.unsupported = True
 
-flags = "--target=x86_64-unknown-linux-gnu -nostdlib -mllvm -x86-asm-syntax=att"
+flags = "--target=x86_64-unknown-linux-gnu -nostdlib"
 
 config.substitutions.insert(0, ("%cflags", f"%cflags {flags}"))
 config.substitutions.insert(0, ("%cxxflags", f"%cxxflags {flags}"))
diff --git a/bolt/test/lit.local.cfg b/bolt/test/lit.local.cfg
index 8a61d11f5825..d6941eced6d5 100644
--- a/bolt/test/lit.local.cfg
+++ b/bolt/test/lit.local.cfg
@@ -7,5 +7,10 @@ if not "linux" in host_triple:
 common_linker_flags = "-fuse-ld=lld -Wl,--unresolved-symbols=ignore-all -Wl,--build-id=none -pie"
 flags = f"--target={host_triple} -fPIE {common_linker_flags}"
 
+# Our files use x86 AT&T assembly throughout.
+# Enable it explicitly so any local Clang preference for Intel syntax gets overriden.
+if "x86-registered-target" in config.available_features:
+  flags += " -mllvm -x86-asm-syntax=att"
+
 config.substitutions.insert(0, ("%cflags", f"%cflags {flags}"))
 config.substitutions.insert(0, ("%cxxflags", f"%cxxflags {flags}"))