diff --git a/git-gui.sh b/git-gui.sh
index 703175975..153f85da0 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -3017,19 +3017,11 @@ blame {
 	set jump_spec {}
 	set is_path 0
 	foreach a $argv {
-		if {[file exists $a]} {
-			if {$path ne {}} usage
-			set path [normalize_relpath $a]
-			break
-		} elseif {[file exists $_prefix$a]} {
-			if {$path ne {}} usage
-			set path [normalize_relpath $_prefix$a]
-			break
-		}
+		set p [file join $_prefix $a]
 
-		if {$is_path} {
+		if {$is_path || [file exists $p]} {
 			if {$path ne {}} usage
-			set path [normalize_relpath $_prefix$a]
+			set path [normalize_relpath $p]
 			break
 		} elseif {$a eq {--}} {
 			if {$path ne {}} {