diff --git a/glib/gbase64.c b/glib/gbase64.c
index d3416e310..baddae098 100644
--- a/glib/gbase64.c
+++ b/glib/gbase64.c
@@ -100,7 +100,7 @@ g_base64_encode_step (const guchar *in,
   char *outptr;
   const guchar *inptr;
 
-  g_return_val_if_fail (in != NULL, 0);
+  g_return_val_if_fail (in != NULL || len == 0, 0);
   g_return_val_if_fail (out != NULL, 0);
   g_return_val_if_fail (state != NULL, 0);
   g_return_val_if_fail (save != NULL, 0);
@@ -244,7 +244,7 @@ g_base64_encode_close (gboolean  break_lines,
 
 /**
  * g_base64_encode:
- * @data: (array length=len) (element-type guint8): the binary data to encode
+ * @data: (array length=len) (element-type guint8) (nullable): the binary data to encode
  * @len: the length of @data
  *
  * Encode a sequence of binary data into its Base-64 stringified
@@ -334,7 +334,7 @@ g_base64_decode_step (const gchar  *in,
   unsigned int v;
   int i;
 
-  g_return_val_if_fail (in != NULL, 0);
+  g_return_val_if_fail (in != NULL || len == 0, 0);
   g_return_val_if_fail (out != NULL, 0);
   g_return_val_if_fail (state != NULL, 0);
   g_return_val_if_fail (save != NULL, 0);
@@ -390,7 +390,7 @@ g_base64_decode_step (const gchar  *in,
 
 /**
  * g_base64_decode:
- * @text: zero-terminated string with base64 text to decode
+ * @text: (not nullable): zero-terminated string with base64 text to decode
  * @out_len: (out): The length of the decoded data is written here
  *
  * Decode a sequence of Base-64 encoded text into binary data.  Note
diff --git a/glib/tests/base64.c b/glib/tests/base64.c
index 86875a29b..6091d1eed 100644
--- a/glib/tests/base64.c
+++ b/glib/tests/base64.c
@@ -406,6 +406,42 @@ test_base64_decode_smallblock (gconstpointer blocksize_p)
     }
 }
 
+/* Test that calling g_base64_encode (NULL, 0) returns correct output. This is
+ * as per the first test vector in RFC 4648 §10.
+ * https://tools.ietf.org/html/rfc4648#section-10 */
+static void
+test_base64_encode_empty (void)
+{
+  gchar *encoded = NULL;
+
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/issues/1698");
+
+  encoded = g_base64_encode (NULL, 0);
+  g_assert_cmpstr (encoded, ==, "");
+  g_free (encoded);
+
+  encoded = g_base64_encode ((const guchar *) "", 0);
+  g_assert_cmpstr (encoded, ==, "");
+  g_free (encoded);
+}
+
+/* Test that calling g_base64_decode ("", *) returns correct output. This is
+ * as per the first test vector in RFC 4648 §10. Note that calling
+ * g_base64_decode (NULL, *) is not allowed.
+ * https://tools.ietf.org/html/rfc4648#section-10 */
+static void
+test_base64_decode_empty (void)
+{
+  guchar *decoded = NULL;
+  gsize decoded_len;
+
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/issues/1698");
+
+  decoded = g_base64_decode ("", &decoded_len);
+  g_assert_cmpstr ((gchar *) decoded, ==, "");
+  g_assert_cmpuint (decoded_len, ==, 0);
+  g_free (decoded);
+}
 
 int
 main (int argc, char *argv[])
@@ -455,5 +491,8 @@ main (int argc, char *argv[])
   g_test_add_data_func ("/base64/incremental/smallblock/4", GINT_TO_POINTER(4),
                         test_base64_decode_smallblock);
 
+  g_test_add_func ("/base64/encode/empty", test_base64_encode_empty);
+  g_test_add_func ("/base64/decode/empty", test_base64_decode_empty);
+
   return g_test_run ();
 }