diff --git a/source/blender/editors/io/io_alembic.c b/source/blender/editors/io/io_alembic.c
index 87923d9fdf8..0e8e0f83597 100644
--- a/source/blender/editors/io/io_alembic.c
+++ b/source/blender/editors/io/io_alembic.c
@@ -282,7 +282,7 @@ void WM_OT_alembic_export(wmOperatorType *ot)
   ot->poll = WM_operator_winactive;
   ot->ui = wm_alembic_export_draw;
   ot->check = wm_alembic_export_check;
-  ot->flag |= OPTYPE_PRESET;
+  ot->flag = OPTYPE_PRESET;
 
   WM_operator_properties_filesel(ot,
                                  FILE_TYPE_FOLDER | FILE_TYPE_ALEMBIC,
diff --git a/source/blender/editors/io/io_collada.c b/source/blender/editors/io/io_collada.c
index dc62212bf53..c491e7a5815 100644
--- a/source/blender/editors/io/io_collada.c
+++ b/source/blender/editors/io/io_collada.c
@@ -468,7 +468,7 @@ void WM_OT_collada_export(wmOperatorType *ot)
   ot->poll = WM_operator_winactive;
   ot->check = wm_collada_export_check;
 
-  ot->flag |= OPTYPE_PRESET;
+  ot->flag = OPTYPE_PRESET;
 
   ot->ui = wm_collada_export_draw;
 
@@ -786,7 +786,7 @@ void WM_OT_collada_import(wmOperatorType *ot)
   ot->exec = wm_collada_import_exec;
   ot->poll = WM_operator_winactive;
 
-  // ot->flag |= OPTYPE_PRESET;
+  // ot->flag = OPTYPE_PRESET;
 
   ot->ui = wm_collada_import_draw;
 
diff --git a/source/blender/editors/io/io_obj.c b/source/blender/editors/io/io_obj.c
index 5537b2575d8..59e8c20da04 100644
--- a/source/blender/editors/io/io_obj.c
+++ b/source/blender/editors/io/io_obj.c
@@ -261,7 +261,7 @@ void WM_OT_obj_export(struct wmOperatorType *ot)
   ot->ui = wm_obj_export_draw;
   ot->check = wm_obj_export_check;
 
-  ot->flag |= OPTYPE_PRESET;
+  ot->flag = OPTYPE_PRESET;
 
   WM_operator_properties_filesel(ot,
                                  FILE_TYPE_FOLDER,
diff --git a/source/blender/editors/io/io_usd.c b/source/blender/editors/io/io_usd.c
index 8a24b48be5e..45d658d5b25 100644
--- a/source/blender/editors/io/io_usd.c
+++ b/source/blender/editors/io/io_usd.c
@@ -216,8 +216,7 @@ void WM_OT_usd_export(struct wmOperatorType *ot)
   ot->ui = wm_usd_export_draw;
   ot->check = wm_usd_export_check;
 
-  ot->flag = OPTYPE_REGISTER; /* No UNDO possible. */
-  ot->flag |= OPTYPE_PRESET;
+  ot->flag = OPTYPE_REGISTER | OPTYPE_PRESET; /* No UNDO possible. */
 
   WM_operator_properties_filesel(ot,
                                  FILE_TYPE_FOLDER | FILE_TYPE_USD,
diff --git a/source/blender/editors/space_clip/clip_ops.c b/source/blender/editors/space_clip/clip_ops.c
index e61c264ca06..f5bf850791a 100644
--- a/source/blender/editors/space_clip/clip_ops.c
+++ b/source/blender/editors/space_clip/clip_ops.c
@@ -777,7 +777,7 @@ void CLIP_OT_view_zoom_in(wmOperatorType *ot)
   ot->poll = ED_space_clip_view_clip_poll;
 
   /* flags */
-  ot->flag |= OPTYPE_LOCK_BYPASS;
+  ot->flag = OPTYPE_LOCK_BYPASS;
 
   /* properties */
   prop = RNA_def_float_vector(ot->srna,
@@ -834,7 +834,7 @@ void CLIP_OT_view_zoom_out(wmOperatorType *ot)
   ot->poll = ED_space_clip_view_clip_poll;
 
   /* flags */
-  ot->flag |= OPTYPE_LOCK_BYPASS;
+  ot->flag = OPTYPE_LOCK_BYPASS;
 
   /* properties */
   prop = RNA_def_float_vector(ot->srna,
@@ -883,7 +883,7 @@ void CLIP_OT_view_zoom_ratio(wmOperatorType *ot)
   ot->poll = ED_space_clip_view_clip_poll;
 
   /* flags */
-  ot->flag |= OPTYPE_LOCK_BYPASS;
+  ot->flag = OPTYPE_LOCK_BYPASS;
 
   /* properties */
   RNA_def_float(ot->srna,
diff --git a/source/blender/editors/space_outliner/outliner_select.cc b/source/blender/editors/space_outliner/outliner_select.cc
index bd6d3d89706..877e0fc325c 100644
--- a/source/blender/editors/space_outliner/outliner_select.cc
+++ b/source/blender/editors/space_outliner/outliner_select.cc
@@ -1693,7 +1693,7 @@ void OUTLINER_OT_item_activate(wmOperatorType *ot)
 
   ot->poll = ED_operator_outliner_active;
 
-  ot->flag |= OPTYPE_REGISTER | OPTYPE_UNDO;
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
   PropertyRNA *prop;
   prop = RNA_def_boolean(ot->srna, "extend", false, "Extend", "Extend selection for activation");
@@ -2028,7 +2028,7 @@ void OUTLINER_OT_select_walk(wmOperatorType *ot)
   ot->invoke = outliner_walk_select_invoke;
   ot->poll = ED_operator_outliner_active;
 
-  ot->flag |= OPTYPE_REGISTER | OPTYPE_UNDO;
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
   /* properties */
   PropertyRNA *prop;
diff --git a/source/blender/editors/space_outliner/outliner_tools.cc b/source/blender/editors/space_outliner/outliner_tools.cc
index bfb4c7251a8..475d02020d0 100644
--- a/source/blender/editors/space_outliner/outliner_tools.cc
+++ b/source/blender/editors/space_outliner/outliner_tools.cc
@@ -1954,7 +1954,7 @@ void OUTLINER_OT_delete(wmOperatorType *ot)
   ot->poll = ED_operator_outliner_active;
 
   /* flags */
-  ot->flag |= OPTYPE_REGISTER | OPTYPE_UNDO;
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 
   /* properties */
   PropertyRNA *prop = RNA_def_boolean(
diff --git a/source/blender/windowmanager/intern/wm_files_link.c b/source/blender/windowmanager/intern/wm_files_link.c
index b41ffb4cfc2..f2c41dada48 100644
--- a/source/blender/windowmanager/intern/wm_files_link.c
+++ b/source/blender/windowmanager/intern/wm_files_link.c
@@ -438,7 +438,7 @@ void WM_OT_link(wmOperatorType *ot)
   ot->exec = wm_link_append_exec;
   ot->poll = wm_link_append_poll;
 
-  ot->flag |= OPTYPE_UNDO;
+  ot->flag = OPTYPE_UNDO;
 
   WM_operator_properties_filesel(ot,
                                  FILE_TYPE_FOLDER | FILE_TYPE_BLENDER | FILE_TYPE_BLENDERLIB,
@@ -462,7 +462,7 @@ void WM_OT_append(wmOperatorType *ot)
   ot->exec = wm_link_append_exec;
   ot->poll = wm_link_append_poll;
 
-  ot->flag |= OPTYPE_UNDO;
+  ot->flag = OPTYPE_UNDO;
 
   WM_operator_properties_filesel(ot,
                                  FILE_TYPE_FOLDER | FILE_TYPE_BLENDER | FILE_TYPE_BLENDERLIB,
@@ -803,7 +803,7 @@ void WM_OT_lib_relocate(wmOperatorType *ot)
   ot->invoke = wm_lib_relocate_invoke;
   ot->exec = wm_lib_relocate_exec;
 
-  ot->flag |= OPTYPE_UNDO;
+  ot->flag = OPTYPE_UNDO;
 
   prop = RNA_def_string(ot->srna, "library", NULL, MAX_NAME, "Library", "Library to relocate");
   RNA_def_property_flag(prop, PROP_HIDDEN);
@@ -833,7 +833,7 @@ void WM_OT_lib_reload(wmOperatorType *ot)
 
   ot->exec = wm_lib_reload_exec;
 
-  ot->flag |= OPTYPE_UNDO;
+  ot->flag = OPTYPE_UNDO;
 
   prop = RNA_def_string(ot->srna, "library", NULL, MAX_NAME, "Library", "Library to reload");
   RNA_def_property_flag(prop, PROP_HIDDEN);