--- gcc/ada/exp_aggr.adb
+++ gcc/ada/exp_aggr.adb
@@ -3103,6 +3103,13 @@ package body Exp_Aggr is
               Make_Selected_Component (Loc,
                 Prefix        => New_Copy_Tree (Lhs),
                 Selector_Name => Make_Identifier (Loc, Chars (Expr))));
+
+            --  The generated code will be reanalyzed, but if the reference
+            --  to the discriminant appears within an already analyzed
+            --  expression (e.g. a conditional) we must set its proper entity
+            --  now. Context is an initialization procedure.
+
+            Analyze (Expr);
          end if;
 
          return OK;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/discr58.adb
@@ -0,0 +1,33 @@
+--  { dg-do compile }
+
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure Discr58 is
+
+   type Field(Flag : Boolean := True) is record
+      case Flag is
+         when True  => Param1 : Boolean := False;
+         when False => Param2 : Boolean := True;
+      end case;
+   end record;
+
+   type Header(Flag : Boolean := True) is record
+      Param3 : Integer     := 0;
+      Params : Field(Flag) := (if Flag = True then
+                                  (Flag => True, others => <>)
+                               else
+                                  (Flag => False, others => <>));
+   end record;
+
+   type Message(Flag : Boolean) is record
+
+      -- This assignment crashes GNAT
+      The_Header : Header(Flag) := Header'(Flag => True, others => <>);
+   end record;
+
+   It : Message (True);
+begin
+   Put_Line("Hello World");
+   Put_Line (Boolean'Image (It.The_Header.Flag));
+   Put_Line (Boolean'Image (It.The_Header.Params.Flag));
+end Discr58;
\ No newline at end of file