Index: lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
===================================================================
--- lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -5162,15 +5162,9 @@
 /// parseDirectiveArchExtension
 ///   ::= .arch_extension [no]feature
 bool AArch64AsmParser::parseDirectiveArchExtension(SMLoc L) {
-  MCAsmParser &Parser = getParser();
-
-  if (getLexer().isNot(AsmToken::Identifier))
-    return Error(getLexer().getLoc(), "expected architecture extension name");
+  SMLoc ExtLoc = getLoc();
 
-  const AsmToken &Tok = Parser.getTok();
-  StringRef Name = Tok.getString();
-  SMLoc ExtLoc = Tok.getLoc();
-  Lex();
+  StringRef Name = getParser().parseStringToEndOfStatement().trim();
 
   if (parseToken(AsmToken::EndOfStatement,
                  "unexpected token in '.arch_extension' directive"))
Index: test/MC/AArch64/directive-arch_extension-negative.s
===================================================================
--- /dev/null
+++ test/MC/AArch64/directive-arch_extension-negative.s
@@ -0,0 +1,10 @@
+// RUN: not llvm-mc -triple aarch64 -filetype asm -o - %s 2>&1 | FileCheck %s
+
+    .arch_extension axp64
+# CHECK: error: unknown architectural extension: axp64
+# CHECK-NEXT: .arch_extension axp64
+
+    .arch_extension notlb-rmi
+    tlbi vmalle1os
+# CHECK: error: TLBI VMALLE1OS requires tlb-rmi
+# CHECK-NEXT:   tlbi vmalle1os
Index: test/MC/AArch64/directive-arch_extension.s
===================================================================
--- /dev/null
+++ test/MC/AArch64/directive-arch_extension.s
@@ -0,0 +1,5 @@
+// RUN: llvm-mc -triple aarch64 -filetype asm -o - %s | FileCheck %s
+
+    .arch_extension tlb-rmi
+    tlbi vmalle1os
+// CHECK: tlbi vmalle1os