diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 35072e85db..55bdd14895 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-17  Tom Tromey  <tom@tromey.com>
+
+	* dwarf2read.c (quirk_rust_enum): Conditionally drop the
+	discriminant field.
+
 2018-04-17  Tom Tromey  <tom@tromey.com>
 
 	* dwarf2read.c (quirk_rust_enum): Handle unions correctly.
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 0d3af00c46..4207e4c531 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -10079,10 +10079,13 @@ quirk_rust_enum (struct type *type, struct objfile *objfile)
 	  if (iter != discriminant_map.end ())
 	    disc->discriminants[i] = iter->second;
 
-	  /* Remove the discriminant field.  */
+	  /* Remove the discriminant field, if it exists.  */
 	  struct type *sub_type = TYPE_FIELD_TYPE (union_type, i);
-	  --TYPE_NFIELDS (sub_type);
-	  ++TYPE_FIELDS (sub_type);
+	  if (TYPE_NFIELDS (sub_type) > 0)
+	    {
+	      --TYPE_NFIELDS (sub_type);
+	      ++TYPE_FIELDS (sub_type);
+	    }
 	  TYPE_FIELD_NAME (union_type, i) = variant_name;
 	  TYPE_NAME (sub_type)
 	    = rust_fully_qualify (&objfile->objfile_obstack,