Index: src/base64.m
==================================================================
--- src/base64.m
+++ src/base64.m
@@ -102,10 +102,13 @@
 	const uint8_t *buf = (const uint8_t*)str;
 	size_t i;
 
 	if ((len & 3) != 0)
 		return NO;
+
+	if ([data itemSize] != 1)
+		return NO;
 
 	for (i = 0; i < len; i += 4) {
 		uint32_t sb = 0;
 		uint8_t cnt = 3;
 		char db[3];