diff --git a/lib/Target/X86/AsmParser/X86AsmParser.cpp b/lib/Target/X86/AsmParser/X86AsmParser.cpp
index aa857f087d8..c370371e864 100644
--- a/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -1246,6 +1246,7 @@ static unsigned getIntelMemOperandSize(StringRef OpStr) {
     .Cases("XWORD", "xword", 80)
     .Cases("XMMWORD", "xmmword", 128)
     .Cases("YMMWORD", "ymmword", 256)
+    .Cases("ZMMWORD", "zmmword", 512)
     .Default(0);
   return Size;
 }
diff --git a/test/MC/X86/intel-syntax-avx512.s b/test/MC/X86/intel-syntax-avx512.s
new file mode 100644
index 00000000000..b382994a097
--- /dev/null
+++ b/test/MC/X86/intel-syntax-avx512.s
@@ -0,0 +1,5 @@
+// RUN: llvm-mc -triple x86_64-unknown-unknown -x86-asm-syntax=intel -mcpu=knl --show-encoding %s | FileCheck %s
+
+// CHECK: vaddps (%rax), %zmm1, %zmm1
+// CHECK: encoding: [0x62,0xf1,0x74,0x48,0x58,0x08]
+vaddps zmm1, zmm1, zmmword ptr [rax]