diff --git a/git-gui.sh b/git-gui.sh
index b70e1598dc0..5404f7e4b52 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -699,7 +699,7 @@ proc apply_config {} {
 
 set default_config(branch.autosetupmerge) true
 set default_config(merge.tool) {}
-set default_config(merge.keepbackup) true
+set default_config(mergetool.keepbackup) true
 set default_config(merge.diffstat) true
 set default_config(merge.summary) false
 set default_config(merge.verbosity) 2
diff --git a/lib/mergetool.tcl b/lib/mergetool.tcl
index 3e1b42beb0d..3fe90e69700 100644
--- a/lib/mergetool.tcl
+++ b/lib/mergetool.tcl
@@ -382,7 +382,7 @@ proc merge_tool_finish {fd} {
 		delete_temp_files $mtool_tmpfiles
 		ui_status [mc "Merge tool failed."]
 	} else {
-		if {[is_config_true merge.keepbackup]} {
+		if {[is_config_true mergetool.keepbackup]} {
 			file rename -force -- $backup "$mtool_target.orig"
 		}