diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 188bb1e8539..9b905ee091b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2020-11-04  Tom Tromey  <tromey@adacore.com>
+
+	* ada-lang.c (to_fixed_array_type): Error if
+	decode_constrained_packed_array_type returns NULL.
+
 2020-11-04  Tom Tromey  <tromey@adacore.com>
 
 	* dwarf2/leb.h (read_3_bytes): Use bfd_get_24.
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index a1f5d93fee3..941b35f6081 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -8350,7 +8350,11 @@ to_fixed_array_type (struct type *type0, struct value *dval,
 
   constrained_packed_array_p = ada_is_constrained_packed_array_type (type0);
   if (constrained_packed_array_p)
-    type0 = decode_constrained_packed_array_type (type0);
+    {
+      type0 = decode_constrained_packed_array_type (type0);
+      if (type0 == nullptr)
+	error (_("could not decode constrained packed array type"));
+    }
 
   index_type_desc = ada_find_parallel_type (type0, xa_suffix);