--- gcc/ada/checks.adb
+++ gcc/ada/checks.adb
@@ -7429,6 +7429,19 @@ package body Checks is
          return;
       end if;
 
+      --  Entities declared in Lock_free protected types must be treated
+      --  as volatile, and we must inhibit validity checks to prevent
+      --  improper constant folding.
+
+      if Is_Entity_Name (Expr)
+        and then Is_Subprogram (Scope (Entity (Expr)))
+        and then Present (Protected_Subprogram (Scope (Entity (Expr))))
+        and then Uses_Lock_Free
+           (Scope (Protected_Subprogram (Scope (Entity (Expr)))))
+      then
+         return;
+      end if;
+
       --  If we have a checked conversion, then validity check applies to
       --  the expression inside the conversion, not the result, since if
       --  the expression inside is valid, then so is the conversion result.

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/prot7.adb
@@ -0,0 +1,22 @@
+--  { dg-do compile }
+--  { dg-options "-gnatwa -gnatVa" }
+
+package body Prot7 is
+   protected body Default_Slice is
+      function Get return Instance_Pointer is
+      begin
+         return Default;
+      end Get;
+
+      procedure Set (
+        Discard : in out Boolean;
+        Slice   : in     Instance_Pointer
+      ) is
+      begin
+         Discard := Default /= null;
+         if not Discard then
+            Default := Slice;
+         end if;
+      end Set;
+   end Default_Slice;
+end Prot7;

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/prot7.ads
@@ -0,0 +1,16 @@
+package Prot7 is
+   type Instance_Pointer is access Integer;
+
+   protected Default_Slice
+        with Lock_Free
+   is
+      function Get return Instance_Pointer;
+
+      procedure Set (
+        Discard : in out Boolean;
+        Slice   : in     Instance_Pointer
+      );
+   private
+      Default : Instance_Pointer;
+   end Default_Slice;
+end Prot7;