diff --git a/libs/ardour/rb_effect.cc b/libs/ardour/rb_effect.cc
index 428490b2d1..070c96c00f 100644
--- a/libs/ardour/rb_effect.cc
+++ b/libs/ardour/rb_effect.cc
@@ -360,7 +360,7 @@ RBEffect::run (boost::shared_ptr<Region> r, Progress* progress)
 		/* multiply the old (possibly previously stretched) region length by the extra
 		 * stretch this time around to get its new length. this is a non-music based edit atm.
 		 */
-		(*x)->set_length ((*x)->length ().scale (tsr.time_fraction));
+		(*x)->set_length_unchecked ((*x)->length ().scale (tsr.time_fraction));
 		(*x)->set_whole_file (true);
 	}
 
diff --git a/libs/ardour/st_stretch.cc b/libs/ardour/st_stretch.cc
index 6e703a5b46..4313616d8f 100644
--- a/libs/ardour/st_stretch.cc
+++ b/libs/ardour/st_stretch.cc
@@ -304,7 +304,7 @@ STStretch::run (boost::shared_ptr<Region> r, Progress* progress)
 		/* multiply the old (possibly previously stretched) region length by the extra
 		 * stretch this time around to get its new length. this is a non-music based edit atm.
 		 */
-		(*x)->set_length ((*x)->length ().scale (tsr.time_fraction));
+		(*x)->set_length_unchecked ((*x)->length ().scale (tsr.time_fraction));
 		(*x)->set_whole_file (true);
 	}