diff --git a/libnm-core/tests/test-general.c b/libnm-core/tests/test-general.c
index 88eb4bc85f..da7ea7b1f8 100644
--- a/libnm-core/tests/test-general.c
+++ b/libnm-core/tests/test-general.c
@@ -6206,7 +6206,9 @@ _test_find_binary_search_do_uint32 (const int *int_array, gsize len)
 	const int OFFSET = 100;
 	const int NEEDLE = 0 + OFFSET;
 	gssize expected_result = -1;
-	guint32 array[len];
+	guint32 array[30];
+
+	g_assert (len <= G_N_ELEMENTS (array));
 
 	/* the test data has negative values. Shift them... */
 	for (idx = 0; idx < len; idx++) {
diff --git a/src/nm-ip4-config.c b/src/nm-ip4-config.c
index 1f98ed08c4..33d1f27507 100644
--- a/src/nm-ip4-config.c
+++ b/src/nm-ip4-config.c
@@ -2879,9 +2879,9 @@ nm_ip4_config_equal (const NMIP4Config *a, const NMIP4Config *b)
 {
 	GChecksum *a_checksum = g_checksum_new (G_CHECKSUM_SHA1);
 	GChecksum *b_checksum = g_checksum_new (G_CHECKSUM_SHA1);
-	gsize a_len = g_checksum_type_get_length (G_CHECKSUM_SHA1);
-	gsize b_len = g_checksum_type_get_length (G_CHECKSUM_SHA1);
-	guchar a_data[a_len], b_data[b_len];
+	guchar a_data[20], b_data[20];
+	gsize a_len = sizeof (a_data);
+	gsize b_len = sizeof (b_data);
 	gboolean equal;
 
 	if (a)
@@ -2892,7 +2892,8 @@ nm_ip4_config_equal (const NMIP4Config *a, const NMIP4Config *b)
 	g_checksum_get_digest (a_checksum, a_data, &a_len);
 	g_checksum_get_digest (b_checksum, b_data, &b_len);
 
-	g_assert (a_len == b_len);
+	nm_assert (a_len == sizeof (a_data));
+	nm_assert (b_len == sizeof (b_data));
 	equal = !memcmp (a_data, b_data, a_len);
 
 	g_checksum_free (a_checksum);
diff --git a/src/nm-ip6-config.c b/src/nm-ip6-config.c
index 7c6b0ee604..d2a08d0ceb 100644
--- a/src/nm-ip6-config.c
+++ b/src/nm-ip6-config.c
@@ -2477,9 +2477,9 @@ nm_ip6_config_equal (const NMIP6Config *a, const NMIP6Config *b)
 {
 	GChecksum *a_checksum = g_checksum_new (G_CHECKSUM_SHA1);
 	GChecksum *b_checksum = g_checksum_new (G_CHECKSUM_SHA1);
-	gsize a_len = g_checksum_type_get_length (G_CHECKSUM_SHA1);
-	gsize b_len = g_checksum_type_get_length (G_CHECKSUM_SHA1);
-	guchar a_data[a_len], b_data[b_len];
+	guchar a_data[20], b_data[20];
+	gsize a_len = sizeof (a_data);
+	gsize b_len = sizeof (b_data);
 	gboolean equal;
 
 	if (a)
@@ -2490,7 +2490,8 @@ nm_ip6_config_equal (const NMIP6Config *a, const NMIP6Config *b)
 	g_checksum_get_digest (a_checksum, a_data, &a_len);
 	g_checksum_get_digest (b_checksum, b_data, &b_len);
 
-	g_assert (a_len == b_len);
+	nm_assert (a_len == sizeof (a_data));
+	nm_assert (b_len == sizeof (b_data));
 	equal = !memcmp (a_data, b_data, a_len);
 
 	g_checksum_free (a_checksum);