diff --git a/lib/Demangle/MicrosoftDemangle.cpp b/lib/Demangle/MicrosoftDemangle.cpp
index 882913a9863..2b41c0037f9 100644
--- a/lib/Demangle/MicrosoftDemangle.cpp
+++ b/lib/Demangle/MicrosoftDemangle.cpp
@@ -276,6 +276,10 @@ Demangler::demangleSpecialTableSymbolNode(StringView &MangledName,
   SpecialTableSymbolNode *STSN = Arena.alloc<SpecialTableSymbolNode>();
   STSN->Name = QN;
   bool IsMember = false;
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
   char Front = MangledName.popFront();
   if (Front != '6' && Front != '7') {
     Error = true;
diff --git a/test/Demangle/invalid-manglings.test b/test/Demangle/invalid-manglings.test
index eb22d1e0a4c..869d63a274f 100644
--- a/test/Demangle/invalid-manglings.test
+++ b/test/Demangle/invalid-manglings.test
@@ -119,3 +119,13 @@
 ; CHECK-EMPTY:
 ; CHECK-NEXT: ?foo@?$?_
 ; CHECK-NEXT: error: Invalid mangled name
+
+??_R4
+; CHECK-EMPTY:
+; CHECK-NEXT: ??_R4
+; CHECK-NEXT: error: Invalid mangled name
+
+??_R4foo@@
+; CHECK-EMPTY:
+; CHECK-NEXT: ??_R4foo@@
+; CHECK-NEXT: error: Invalid mangled name