diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index b0a4029c94..c6dd71a7bc 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -503,7 +503,7 @@ static void export_marks(char *file)
 
 	f = fopen(file, "w");
 	if (!f)
-		error("Unable to open marks file %s for writing.", file);
+		die_errno("Unable to open marks file %s for writing.", file);
 
 	for (i = 0; i < idnums.size; i++) {
 		if (deco->base && deco->base->type == 1) {
diff --git a/git-difftool.perl b/git-difftool.perl
index d975d072db..adc42de875 100755
--- a/git-difftool.perl
+++ b/git-difftool.perl
@@ -78,11 +78,13 @@ sub generate_command
 			next;
 		}
 		if ($arg eq '-g' || $arg eq '--gui') {
-			my $tool = Git::command_oneline('config',
-			                                'diff.guitool');
-			if (length($tool)) {
-				$ENV{GIT_DIFF_TOOL} = $tool;
-			}
+			eval {
+				my $tool = Git::command_oneline('config',
+				                                'diff.guitool');
+				if (length($tool)) {
+					$ENV{GIT_DIFF_TOOL} = $tool;
+				}
+			};
 			next;
 		}
 		if ($arg eq '-y' || $arg eq '--no-prompt') {
diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index 19c72f55bf..1de83ef98f 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -92,6 +92,15 @@ test_expect_success 'difftool honors --gui' '
 	restore_test_defaults
 '
 
+test_expect_success 'difftool --gui works without configured diff.guitool' '
+	git config diff.tool test-tool &&
+
+	diff=$(git difftool --no-prompt --gui branch) &&
+	test "$diff" = "branch" &&
+
+	restore_test_defaults
+'
+
 # Specify the diff tool using $GIT_DIFF_TOOL
 test_expect_success 'GIT_DIFF_TOOL variable' '
 	git config --unset diff.tool
diff --git a/t/t9350-fast-export.sh b/t/t9350-fast-export.sh
index 356964e53a..d43f37ccaf 100755
--- a/t/t9350-fast-export.sh
+++ b/t/t9350-fast-export.sh
@@ -150,20 +150,22 @@ test_expect_success 'setup submodule' '
 
 	git checkout -f master &&
 	mkdir sub &&
-	cd sub &&
-	git init  &&
-	echo test file > file &&
-	git add file &&
-	git commit -m sub_initial &&
-	cd .. &&
+	(
+		cd sub &&
+		git init  &&
+		echo test file > file &&
+		git add file &&
+		git commit -m sub_initial
+	) &&
 	git submodule add "`pwd`/sub" sub &&
 	git commit -m initial &&
 	test_tick &&
-	cd sub &&
-	echo more data >> file &&
-	git add file &&
-	git commit -m sub_second &&
-	cd .. &&
+	(
+		cd sub &&
+		echo more data >> file &&
+		git add file &&
+		git commit -m sub_second
+	) &&
 	git add sub &&
 	git commit -m second
 
@@ -264,19 +266,20 @@ test_expect_success 'cope with tagger-less tags' '
 
 test_expect_success 'setup for limiting exports by PATH' '
 	mkdir limit-by-paths &&
-	cd limit-by-paths &&
-	git init &&
-	echo hi > there &&
-	git add there &&
-	git commit -m "First file" &&
-	echo foo > bar &&
-	git add bar &&
-	git commit -m "Second file" &&
-	git tag -a -m msg mytag &&
-	echo morefoo >> bar &&
-	git add bar &&
-	git commit -m "Change to second file" &&
-	cd ..
+	(
+		cd limit-by-paths &&
+		git init &&
+		echo hi > there &&
+		git add there &&
+		git commit -m "First file" &&
+		echo foo > bar &&
+		git add bar &&
+		git commit -m "Second file" &&
+		git tag -a -m msg mytag &&
+		echo morefoo >> bar &&
+		git add bar &&
+		git commit -m "Change to second file"
+	)
 '
 
 cat > limit-by-paths/expected << EOF
@@ -297,10 +300,11 @@ M 100644 :1 there
 EOF
 
 test_expect_success 'dropping tag of filtered out object' '
+(
 	cd limit-by-paths &&
 	git fast-export --tag-of-filtered-object=drop mytag -- there > output &&
-	test_cmp output expected &&
-	cd ..
+	test_cmp output expected
+)
 '
 
 cat >> limit-by-paths/expected << EOF
@@ -313,10 +317,11 @@ msg
 EOF
 
 test_expect_success 'rewriting tag of filtered out object' '
+(
 	cd limit-by-paths &&
 	git fast-export --tag-of-filtered-object=rewrite mytag -- there > output &&
-	test_cmp output expected &&
-	cd ..
+	test_cmp output expected
+)
 '
 
 cat > limit-by-paths/expected << EOF
@@ -343,13 +348,13 @@ M 100644 :2 there
 EOF
 
 test_expect_failure 'no exact-ref revisions included' '
-	cd limit-by-paths &&
-	git fast-export master~2..master~1 > output &&
-	test_cmp output expected &&
-	cd ..
+	(
+		cd limit-by-paths &&
+		git fast-export master~2..master~1 > output &&
+		test_cmp output expected
+	)
 '
 
-
 test_expect_success 'set-up a few more tags for tag export tests' '
 	git checkout -f master &&
 	HEAD_TREE=`git show -s --pretty=raw HEAD | grep tree | sed "s/tree //"` &&