diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
--- a/clang/lib/AST/StmtPrinter.cpp
+++ b/clang/lib/AST/StmtPrinter.cpp
@@ -1170,6 +1170,10 @@
   case BuiltinType::ULong:     OS << "UL"; break;
   case BuiltinType::LongLong:  OS << "LL"; break;
   case BuiltinType::ULongLong: OS << "ULL"; break;
+  case BuiltinType::Int128:
+    break; // no suffix.
+  case BuiltinType::UInt128:
+    break; // no suffix.
   }
 }
 
diff --git a/clang/test/AST/ast-print-int128.cpp b/clang/test/AST/ast-print-int128.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/AST/ast-print-int128.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -ast-print -std=c++20 %s -o - | FileCheck %s
+
+template <bool>
+struct enable_if {
+};
+
+template <__uint128_t x, typename = typename enable_if<x != 0>::type>
+void f();
+
+template <__int128_t>
+void f();
+
+using T = decltype(f<0>());
+
+// CHECK: using T = decltype(f<0>());