diff --git a/lib/Demangle/MicrosoftDemangle.cpp b/lib/Demangle/MicrosoftDemangle.cpp
index 719e716..882913a 100644
--- a/lib/Demangle/MicrosoftDemangle.cpp
+++ b/lib/Demangle/MicrosoftDemangle.cpp
@@ -654,7 +654,10 @@
 IdentifierNode *
 Demangler::demangleFunctionIdentifierCode(StringView &MangledName,
                                           FunctionIdentifierCodeGroup Group) {
-  assert(!MangledName.empty());
+  if (MangledName.empty()) {
+    Error = true;
+    return nullptr;
+  }
   switch (Group) {
   case FunctionIdentifierCodeGroup::Basic:
     switch (char CH = MangledName.popFront()) {
diff --git a/test/Demangle/invalid-manglings.test b/test/Demangle/invalid-manglings.test
index 473b3e4..eb22d1e 100644
--- a/test/Demangle/invalid-manglings.test
+++ b/test/Demangle/invalid-manglings.test
@@ -114,3 +114,8 @@
 ; CHECK-EMPTY:
 ; CHECK-NEXT: ??}
 ; CHECK-NEXT: error: Invalid mangled name
+
+?foo@?$?_
+; CHECK-EMPTY:
+; CHECK-NEXT: ?foo@?$?_
+; CHECK-NEXT: error: Invalid mangled name