diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 52079b4313..5b911af3fd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2018-03-01  Tom Tromey  <tom@tromey.com>
+
+	* dwarf2read.c (alloc_discriminant_info): Fix default_index
+	assertion.  Add assertion for discriminant_index.
+	(quirk_rust_enum): Use correct base type name in univariant case.
+
 2018-03-01  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* record.c (get_call_history_modifiers): Return a
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 9825117fa7..5827ab446c 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -10364,8 +10364,11 @@ alloc_discriminant_info (struct type *type, int discriminant_index,
 			 int default_index)
 {
   gdb_assert (TYPE_CODE (type) == TYPE_CODE_UNION);
+  gdb_assert (discriminant_index == -1
+	      || (discriminant_index >= 0
+		  && discriminant_index < TYPE_NFIELDS (type)));
   gdb_assert (default_index == -1
-	      || (default_index > 0 && default_index < TYPE_NFIELDS (type)));
+	      || (default_index >= 0 && default_index < TYPE_NFIELDS (type)));
 
   TYPE_FLAG_DISCRIMINATED_UNION (type) = 1;
 
@@ -10518,7 +10521,7 @@ quirk_rust_enum (struct type *type, struct objfile *objfile)
       TYPE_FIELD_NAME (union_type, 0) = variant_name;
       TYPE_NAME (field_type)
 	= rust_fully_qualify (&objfile->objfile_obstack,
-			      TYPE_NAME (field_type), variant_name);
+			      TYPE_NAME (type), variant_name);
 
       /* Install the union in the outer struct type.  */
       TYPE_NFIELDS (type) = 1;