diff --git a/src/utils/base64.c b/src/utils/base64.c
index af1307fc4..7366c30d3 100644
--- a/src/utils/base64.c
+++ b/src/utils/base64.c
@@ -48,9 +48,11 @@ unsigned char * base64_encode(const unsigned char *src, size_t len,
 	pos = out;
 	line_len = 0;
 	while (end - in >= 3) {
-		*pos++ = base64_table[in[0] >> 2];
-		*pos++ = base64_table[((in[0] & 0x03) << 4) | (in[1] >> 4)];
-		*pos++ = base64_table[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
+		*pos++ = base64_table[(in[0] >> 2) & 0x3f];
+		*pos++ = base64_table[(((in[0] & 0x03) << 4) |
+				       (in[1] >> 4)) & 0x3f];
+		*pos++ = base64_table[(((in[1] & 0x0f) << 2) |
+				       (in[2] >> 6)) & 0x3f];
 		*pos++ = base64_table[in[2] & 0x3f];
 		in += 3;
 		line_len += 4;