diff --git a/libcxxabi/src/demangle/ItaniumDemangle.h b/libcxxabi/src/demangle/ItaniumDemangle.h
index 85694d9e93a1..afef50b26ca5 100644
--- a/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -98,7 +98,7 @@
     X(BoolExpr) \
     X(StringLiteral) \
     X(LambdaExpr) \
-    X(IntegerCastExpr) \
+    X(EnumLiteral)    \
     X(IntegerLiteral) \
     X(FloatLiteral) \
     X(DoubleLiteral) \
@@ -2036,22 +2036,26 @@ public:
   }
 };
 
-class IntegerCastExpr : public Node {
+class EnumLiteral : public Node {
   // ty(integer)
   const Node *Ty;
   StringView Integer;
 
 public:
-  IntegerCastExpr(const Node *Ty_, StringView Integer_)
-      : Node(KIntegerCastExpr), Ty(Ty_), Integer(Integer_) {}
+  EnumLiteral(const Node *Ty_, StringView Integer_)
+      : Node(KEnumLiteral), Ty(Ty_), Integer(Integer_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Integer); }
 
   void printLeft(OutputStream &S) const override {
-    S += "(";
+    S << "(";
     Ty->print(S);
-    S += ")";
-    S += Integer;
+    S << ")";
+
+    if (Integer[0] == 'n')
+      S << "-" << Integer.dropFront(1);
+    else
+      S << Integer;
   }
 };
 
@@ -4270,12 +4274,12 @@ Node *AbstractManglingParser<Derived, Alloc>::parseExprPrimary() {
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
-    StringView N = parseNumber();
+    StringView N = parseNumber(/*AllowNegative=*/true);
     if (N.empty())
       return nullptr;
     if (!consumeIf('E'))
       return nullptr;
-    return make<IntegerCastExpr>(T, N);
+    return make<EnumLiteral>(T, N);
   }
   }
 }
diff --git a/libcxxabi/test/test_demangle.pass.cpp b/libcxxabi/test/test_demangle.pass.cpp
index edab9ad827e6..2df8ea17511e 100644
--- a/libcxxabi/test/test_demangle.pass.cpp
+++ b/libcxxabi/test/test_demangle.pass.cpp
@@ -29792,6 +29792,8 @@ const char* cases[][2] =
     //   "auto inline_func()::'lambda'<int, int>(int, int) const"
     {"_ZZ11inline_funcvENKUlTyTyT_T0_E_clIiiEEDaS_S0_", "auto inline_func()::'lambda'<typename $T, typename $T0>($T, $T0)::operator()<int, int>($T, $T0) const"},
     {"_ZZ11inline_funcvENKUlTyTyT_T1_T0_E_clIiiiEEDaS_S0_S1_", "auto inline_func()::'lambda'<typename $T, typename $T0>($T, auto, $T0)::operator()<int, int, int>($T, auto, $T0) const"},
+
+    {"_Z1fIL4Enumn1EEvv", "void f<(Enum)-1>()"},
 };
 
 const unsigned N = sizeof(cases) / sizeof(cases[0]);
diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
index 85694d9e93a1..afef50b26ca5 100644
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -98,7 +98,7 @@
     X(BoolExpr) \
     X(StringLiteral) \
     X(LambdaExpr) \
-    X(IntegerCastExpr) \
+    X(EnumLiteral)    \
     X(IntegerLiteral) \
     X(FloatLiteral) \
     X(DoubleLiteral) \
@@ -2036,22 +2036,26 @@ public:
   }
 };
 
-class IntegerCastExpr : public Node {
+class EnumLiteral : public Node {
   // ty(integer)
   const Node *Ty;
   StringView Integer;
 
 public:
-  IntegerCastExpr(const Node *Ty_, StringView Integer_)
-      : Node(KIntegerCastExpr), Ty(Ty_), Integer(Integer_) {}
+  EnumLiteral(const Node *Ty_, StringView Integer_)
+      : Node(KEnumLiteral), Ty(Ty_), Integer(Integer_) {}
 
   template<typename Fn> void match(Fn F) const { F(Ty, Integer); }
 
   void printLeft(OutputStream &S) const override {
-    S += "(";
+    S << "(";
     Ty->print(S);
-    S += ")";
-    S += Integer;
+    S << ")";
+
+    if (Integer[0] == 'n')
+      S << "-" << Integer.dropFront(1);
+    else
+      S << Integer;
   }
 };
 
@@ -4270,12 +4274,12 @@ Node *AbstractManglingParser<Derived, Alloc>::parseExprPrimary() {
     Node *T = getDerived().parseType();
     if (T == nullptr)
       return nullptr;
-    StringView N = parseNumber();
+    StringView N = parseNumber(/*AllowNegative=*/true);
     if (N.empty())
       return nullptr;
     if (!consumeIf('E'))
       return nullptr;
-    return make<IntegerCastExpr>(T, N);
+    return make<EnumLiteral>(T, N);
   }
   }
 }