diff --git a/libiberty/d-demangle.c b/libiberty/d-demangle.c
index 7ded3e2a256..3adf7b562d1 100644
--- a/libiberty/d-demangle.c
+++ b/libiberty/d-demangle.c
@@ -875,7 +875,7 @@ dlang_type (string *decl, const char *mangled, struct dlang_info *info)
       szmods = string_length (&mods);
 
       /* Back referenced function type.  */
-      if (*mangled == 'Q')
+      if (mangled && *mangled == 'Q')
 	mangled = dlang_type_backref (decl, mangled, info, 1);
       else
 	mangled = dlang_function_type (decl, mangled, info);
diff --git a/libiberty/testsuite/d-demangle-expected b/libiberty/testsuite/d-demangle-expected
index c35185c3e1e..799f4724b72 100644
--- a/libiberty/testsuite/d-demangle-expected
+++ b/libiberty/testsuite/d-demangle-expected
@@ -991,9 +991,12 @@ _D88
 _D5__T1aZv
 _D5__T1aZv
 #
+_D00
+_D00
+#
 --format=dlang
-_D00
-_D00
+_D01_D
+_D01_D
 #
 --format=dlang
 _D9223372036854775817