diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 1f490b3efe1..84c2239d209 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,8 @@
+2019-08-19  Bob Duff  <duff@adacore.com>
+
+	* sem_warn.adb (Warn_On_Unreferenced_Entity): Suppress warning
+	on formal parameters of dispatching operations.
+
 2019-08-19  Ed Schonberg  <schonberg@adacore.com>
 
 	* sem_res.adb (Resolve_Call): A call to an expression function
diff --git a/gcc/ada/sem_warn.adb b/gcc/ada/sem_warn.adb
index ca6515c3bcd..8f85057dc0d 100644
--- a/gcc/ada/sem_warn.adb
+++ b/gcc/ada/sem_warn.adb
@@ -4407,11 +4407,31 @@ package body Sem_Warn is
                         E := Body_E;
                      end if;
 
-                     if not Is_Trivial_Subprogram (Scope (E)) then
-                        Error_Msg_NE -- CODEFIX
-                          ("?u?formal parameter & is not referenced!",
-                           E, Spec_E);
-                     end if;
+                     declare
+                        B : constant Node_Id := Parent (Parent (Scope (E)));
+                        S : Entity_Id := Empty;
+                     begin
+                        if Nkind_In (B,
+                                     N_Expression_Function,
+                                     N_Subprogram_Body,
+                                     N_Subprogram_Renaming_Declaration)
+                        then
+                           S := Corresponding_Spec (B);
+                        end if;
+
+                        --  Do not warn for dispatching operations, because
+                        --  that causes too much noise. Also do not warn for
+                        --  trivial subprograms.
+
+                        if (not Present (S)
+                            or else not Is_Dispatching_Operation (S))
+                          and then not Is_Trivial_Subprogram (Scope (E))
+                        then
+                           Error_Msg_NE -- CODEFIX
+                             ("?u?formal parameter & is not referenced!",
+                              E, Spec_E);
+                        end if;
+                     end;
                   end if;
                end if;
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2dd707d36c6..5bafa9d636f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-08-19  Bob Duff  <duff@adacore.com>
+
+	* gnat.dg/warn29.adb, gnat.dg/warn29.ads: New testcase.
+
 2019-08-19  Ed Schonberg  <schonberg@adacore.com>
 
 	* gnat.dg/expr_func9.adb: New testcase.
diff --git a/gcc/testsuite/gnat.dg/warn29.adb b/gcc/testsuite/gnat.dg/warn29.adb
new file mode 100644
index 00000000000..ec3b9eebf6e
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/warn29.adb
@@ -0,0 +1,11 @@
+--  { dg-do compile }
+--  { dg-options "-gnatwa" }
+
+with Text_IO; use Text_IO;
+
+package body Warn29 is
+   procedure P (X : T; Y : Integer) is
+   begin
+      Put_Line ("hello");
+   end P;
+end Warn29;
diff --git a/gcc/testsuite/gnat.dg/warn29.ads b/gcc/testsuite/gnat.dg/warn29.ads
new file mode 100644
index 00000000000..56c202a8c87
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/warn29.ads
@@ -0,0 +1,4 @@
+package Warn29 is
+   type T is tagged null record;
+   procedure P (X : T; Y : Integer);
+end Warn29;