diff --git a/diff.c b/diff.c
index 019fb893a7..c89c15d98e 100644
--- a/diff.c
+++ b/diff.c
@@ -5493,6 +5493,8 @@ static int diff_opt_pickaxe_regex(const struct option *opt,
 	BUG_ON_OPT_NEG(unset);
 	options->pickaxe = arg;
 	options->pickaxe_opts |= DIFF_PICKAXE_KIND_G;
+	if (arg && !*arg)
+		return error(_("-G requires a non-empty argument"));
 	return 0;
 }
 
@@ -5504,6 +5506,8 @@ static int diff_opt_pickaxe_string(const struct option *opt,
 	BUG_ON_OPT_NEG(unset);
 	options->pickaxe = arg;
 	options->pickaxe_opts |= DIFF_PICKAXE_KIND_S;
+	if (arg && !*arg)
+		return error(_("-S requires a non-empty argument"));
 	return 0;
 }
 
diff --git a/t/t4209-log-pickaxe.sh b/t/t4209-log-pickaxe.sh
index a675ace081..0e2f80a268 100755
--- a/t/t4209-log-pickaxe.sh
+++ b/t/t4209-log-pickaxe.sh
@@ -93,6 +93,22 @@ test_expect_success 'usage: --no-pickaxe-regex' '
 	test_cmp expect actual
 '
 
+test_expect_success 'usage: -G and -S with empty argument' '
+	cat >expect <<-\EOF &&
+	error: -S requires a non-empty argument
+	EOF
+
+	test_expect_code 129 git log -S "" 2>actual &&
+	test_cmp expect actual &&
+
+	cat >expect <<-\EOF &&
+	error: -G requires a non-empty argument
+	EOF
+
+	test_expect_code 129 git log -G "" 2>actual &&
+	test_cmp expect actual
+'
+
 test_log	expect_initial	--grep initial
 test_log	expect_nomatch	--grep InItial
 test_log_icase	expect_initial	--grep InItial