diff --git a/git-gui.sh b/git-gui.sh
index 4617f29c267..422d4ff5bd9 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -444,6 +444,8 @@ proc _lappend_nice {cmd_var} {
 		set _nice [_which nice]
 		if {[catch {exec $_nice git version}]} {
 			set _nice {}
+		} elseif {[is_Windows] && [file dirname $_nice] ne [file dirname $::_git]} {
+			set _nice {}
 		}
 	}
 	if {$_nice ne {}} {