diff --git a/setup.c b/setup.c
index 87c21f02e0..2769160527 100644
--- a/setup.c
+++ b/setup.c
@@ -170,6 +170,8 @@ static int is_git_directory(const char *suspect)
 	char path[PATH_MAX];
 	size_t len = strlen(suspect);
 
+	if (PATH_MAX <= len + strlen("/objects"))
+		die("Too long path: %.*s", 60, suspect);
 	strcpy(path, suspect);
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
diff --git a/t/README b/t/README
index b906ceb476..a590142438 100644
--- a/t/README
+++ b/t/README
@@ -451,8 +451,10 @@ library for your script to use.
  - test_must_fail <git-command>
 
    Run a git command and ensure it fails in a controlled way.  Use
-   this instead of "! <git-command>" to fail when git commands
-   segfault.
+   this instead of "! <git-command>".  When git-command dies due to a
+   segfault, test_must_fail diagnoses it as an error; "! <git-command>"
+   treats it as just another expected failure, which would let such a
+   bug go unnoticed.
 
  - test_might_fail <git-command>
 
diff --git a/t/lib-httpd.sh b/t/lib-httpd.sh
index 71effc5bec..e733f6516f 100644
--- a/t/lib-httpd.sh
+++ b/t/lib-httpd.sh
@@ -145,7 +145,7 @@ test_http_push_nonff() {
 		echo "changed" > path2 &&
 		git commit -a -m path2 --amend &&
 
-		!(git push -v origin >output 2>&1) &&
+		test_must_fail git push -v origin >output 2>&1 &&
 		(cd "$REMOTE_REPO" &&
 		 test $HEAD = $(git rev-parse --verify HEAD))
 	'
diff --git a/t/t3700-add.sh b/t/t3700-add.sh
index 47fbf5362f..d03495dc7a 100755
--- a/t/t3700-add.sh
+++ b/t/t3700-add.sh
@@ -268,7 +268,7 @@ test_expect_success 'git add --dry-run of existing changed file' "
 
 test_expect_success 'git add --dry-run of non-existing file' "
 	echo ignored-file >>.gitignore &&
-	! (git add --dry-run track-this ignored-file >actual 2>&1) &&
+	test_must_fail git add --dry-run track-this ignored-file >actual 2>&1 &&
 	echo \"fatal: pathspec 'ignored-file' did not match any files\" | test_cmp - actual
 "
 
@@ -281,7 +281,7 @@ add 'track-this'
 EOF
 
 test_expect_success 'git add --dry-run --ignore-missing of non-existing file' '
-	!(git add --dry-run --ignore-missing track-this ignored-file >actual 2>&1) &&
+	test_must_fail git add --dry-run --ignore-missing track-this ignored-file >actual 2>&1 &&
 	test_cmp expect actual
 '
 
diff --git a/t/t5541-http-push.sh b/t/t5541-http-push.sh
index 504884b9f8..b0c2a2c3ae 100755
--- a/t/t5541-http-push.sh
+++ b/t/t5541-http-push.sh
@@ -128,7 +128,7 @@ test_expect_success 'push fails for non-fast-forward refs unmatched by remote he
 
 	# push master too; this ensures there is at least one '"'push'"' command to
 	# the remote helper and triggers interaction with the helper.
-	!(git push -v origin +master master:retsam >output 2>&1) &&
+	test_must_fail git push -v origin +master master:retsam >output 2>&1 &&
 
 	grep "^ + [a-f0-9]*\.\.\.[a-f0-9]* *master -> master (forced update)$" output &&
 	grep "^ ! \[rejected\] *master -> retsam (non-fast-forward)$" output &&