diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5e9beb9b7a..e6903f2281 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-03-12  Tom Tromey  <tromey@adacore.com>
+
+	* common/ptid.c (null_ptid, minus_one_ptid): Now const.
+	* common/ptid.h (null_ptid, minus_one_ptid): Now const.
+
 2019-03-12  Tom Tromey  <tromey@adacore.com>
 
 	* linux-nat.c (iterate_over_lwps): Update.
diff --git a/gdb/common/ptid.c b/gdb/common/ptid.c
index 93f853af80..c025511a37 100644
--- a/gdb/common/ptid.c
+++ b/gdb/common/ptid.c
@@ -22,5 +22,5 @@
 
 /* See ptid.h for these.  */
 
-ptid_t null_ptid = ptid_t::make_null ();
-ptid_t minus_one_ptid = ptid_t::make_minus_one ();
+ptid_t const null_ptid = ptid_t::make_null ();
+ptid_t const minus_one_ptid = ptid_t::make_minus_one ();
diff --git a/gdb/common/ptid.h b/gdb/common/ptid.h
index 31440c8d7c..f5625a6138 100644
--- a/gdb/common/ptid.h
+++ b/gdb/common/ptid.h
@@ -145,11 +145,11 @@ private:
 
 /* The null or zero ptid, often used to indicate no process. */
 
-extern ptid_t null_ptid;
+extern const ptid_t null_ptid;
 
 /* The (-1,0,0) ptid, often used to indicate either an error condition
    or a "don't care" condition, i.e, "run all threads."  */
 
-extern ptid_t minus_one_ptid;
+extern const ptid_t minus_one_ptid;
 
 #endif /* COMMON_PTID_H */