Index: lib/Target/X86/AsmParser/X86AsmParser.cpp
===================================================================
--- lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -2055,14 +2055,17 @@
         // no errors.
         // Query for the need of further parsing for a {%k<NUM>} mark
         if (!Z || getLexer().is(AsmToken::LCurly)) {
-          const SMLoc StartLoc = Z ? consumeToken() : consumedToken;
+          SMLoc StartLoc = Z ? consumeToken() : consumedToken;
           // Parse an op-mask register mark ({%k<NUM>}), which is now to be
           // expected
-          if (std::unique_ptr<X86Operand> Op = ParseOperand()) {
+          unsigned RegNo;
+          if (!ParseRegister(RegNo, StartLoc, StartLoc) &&
+              X86MCRegisterClasses[X86::VK1RegClassID].contains(RegNo)) {
             if (!getLexer().is(AsmToken::RCurly))
               return Error(getLexer().getLoc(), "Expected } at this point");
             Operands.push_back(X86Operand::CreateToken("{", StartLoc));
-            Operands.push_back(std::move(Op));
+            Operands.push_back(std::move(X86Operand::CreateReg(RegNo, StartLoc,
+                                                               StartLoc)));
             Operands.push_back(X86Operand::CreateToken("}", consumeToken()));
           } else
             return Error(getLexer().getLoc(),
@@ -2072,7 +2075,8 @@
             // Have we've found a parsing error, or found no (expected) {z} mark
             // - report an error
             if (ParseZ(Z, consumeToken()) || !Z)
-              return true;
+              return Error(getLexer().getLoc(),
+                           "Expected a {z} mark at this point");
 
           }
           // '{z}' on its own is meaningless, hence should be ignored.
Index: test/MC/X86/avx512-err.s
===================================================================
--- test/MC/X86/avx512-err.s
+++ test/MC/X86/avx512-err.s
@@ -1,6 +1,11 @@
-// RUN: not llvm-mc -triple x86_64-unknown-unknown -mcpu=knl -mattr=+avx512dq --show-encoding %s 2> %t.err
+// RUN: not llvm-mc -triple x86_64-unknown-unknown -mcpu=knl -mattr=+avx512dq -mattr=+avx512f --show-encoding %s 2> %t.err
 // RUN: FileCheck --check-prefix=ERR < %t.err %s
 
 // ERR: invalid operand for instruction
 vpcmpd $1, %zmm24, %zmm7, %k5{%k0}
 
+// ERR: Expected a {z} mark at this point
+vfmsub213ps %zmm8, %zmm8, %zmm8{%k2} {rn-sae}
+
+// ERR: Expected an op-mask register at this point
+vfmsub213ps %zmm8, %zmm8, %zmm8 {rn-sae}