diff --git a/src/lib/istream-base64-encoder.c b/src/lib/istream-base64-encoder.c
index c1ae2bb2ce..c51fdcda1c 100644
--- a/src/lib/istream-base64-encoder.c
+++ b/src/lib/istream-base64-encoder.c
@@ -158,6 +158,8 @@ i_stream_base64_encoder_stat(struct istream_private *stream,
 	}
 
 	stream->statbuf = *st;
+	if (st->st_size == 0)
+		return 0;
 	
 	/* calculate size of encoded data */
 	size = (st->st_size / 3) * 4 +
diff --git a/src/lib/test-istream-base64-encoder.c b/src/lib/test-istream-base64-encoder.c
index e03effa354..8f9f2fa3b8 100644
--- a/src/lib/test-istream-base64-encoder.c
+++ b/src/lib/test-istream-base64-encoder.c
@@ -11,6 +11,12 @@ static const struct test {
 	bool crlf;
 	const char *output;
 } tests[] = {
+	{ "", 80, FALSE, "" },
+	{ "1", 80, FALSE, "MQ==" },
+	{ "12", 80, FALSE, "MTI=" },
+	{ "123", 80, FALSE, "MTIz" },
+	{ "1234", 80, FALSE, "MTIzNA==" },
+	{ "12345", 80, FALSE, "MTIzNDU=" },
 	{ "hello world", 80, FALSE, "aGVsbG8gd29ybGQ=" },
 	{ "hello world", 4, FALSE, "aGVs\nbG8g\nd29y\nbGQ=" },
 	{ "hello world", 4, TRUE, "aGVs\r\nbG8g\r\nd29y\r\nbGQ=" },