diff --git a/gcc/c-family/c-ada-spec.cc b/gcc/c-family/c-ada-spec.cc
index b50b38775..6c6b5d083 100644
--- a/gcc/c-family/c-ada-spec.cc
+++ b/gcc/c-family/c-ada-spec.cc
@@ -2193,2 +2193,2 @@ dump_ada_node (pretty_printer *buffer, tree node, tree type, int spc,
-	       && !strcmp (IDENTIFIER_POINTER (DECL_NAME (TYPE_NAME (node))),
-			   "__int128")))
+	       && !strncmp (IDENTIFIER_POINTER (DECL_NAME (TYPE_NAME (node))),
+			    "__int128", 8)))
diff --git a/gcc/testsuite/g++.dg/ada-spec/int128-types.C b/gcc/testsuite/g++.dg/ada-spec/int128-types.C
new file mode 100644
index 000000000..0a432e72f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ada-spec/int128-types.C
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-ada-spec-slim" } */
+/* { dg-final { scan-file int128_types_c.ads "subtype Signed_128 is Extensions.Signed_128" } } */
+/* { dg-final { scan-file int128_types_c.ads "subtype Unsigned_128 is Extensions.Unsigned_128" } } */
+
+using Signed_128 = __int128;
+using Unsigned_128 = unsigned __int128;
+
+static const Signed_128 signed_expected
+  = -((static_cast<Signed_128> (1) << 100) + 12345);
+static const Unsigned_128 unsigned_expected
+  = (static_cast<Unsigned_128> (1) << 127)
+    | (static_cast<Unsigned_128> (1) << 80) | 67890;
+
+Signed_128 signed_seed () { return signed_expected; }
+Unsigned_128 unsigned_seed () { return unsigned_expected; }
+
+Signed_128 signed_round_trip (Signed_128 value) { return value; }
+Unsigned_128 unsigned_round_trip (Unsigned_128 value) { return value; }
+
+int signed_matches (Signed_128 value) { return value == signed_expected; }
+int unsigned_matches (Unsigned_128 value) { return value == unsigned_expected; }