diff --git a/git-gui.sh b/git-gui.sh
index 6608116339..a5f31dc391 100755
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -50,26 +50,33 @@ if {$oguirel eq {1}} {
 } elseif {[string match @@* $oguirel]} {
 	set oguilib [file join [file dirname [file normalize $argv0]] lib]
 }
+
 set idx [file join $oguilib tclIndex]
-catch {
-	set fd [open $idx r]
-	if {[gets $fd] eq {# Autogenerated by git-gui Makefile}} {
-		set idx [list]
-		while {[gets $fd n] >= 0} {
-			if {$n ne {} && ![string match #* $n]} {
-				lappend idx $n
-			}
-		}
-	} else {
-		set idx {}
-	}
-	close $fd
+if {[catch {set fd [open $idx r]} err]} {
+	catch {wm withdraw .}
+	tk_messageBox \
+		-icon error \
+		-type ok \
+		-title "git-gui: fatal error" \
+		-message $err
+	exit 1
 }
+if {[gets $fd] eq {# Autogenerated by git-gui Makefile}} {
+	set idx [list]
+	while {[gets $fd n] >= 0} {
+		if {$n ne {} && ![string match #* $n]} {
+			lappend idx $n
+		}
+	}
+} else {
+	set idx {}
+}
+close $fd
+
 if {$idx ne {}} {
 	set loaded [list]
 	foreach p $idx {
 		if {[lsearch -exact $loaded $p] >= 0} continue
-		puts $p
 		source [file join $oguilib $p]
 		lappend loaded $p
 	}