--- mimetic-0.9.8/mimetic/codec/base64.h.old	2014-06-17 08:12:00.000000000 +0000
+++ mimetic-0.9.8/mimetic/codec/base64.h	2018-08-01 05:37:10.280000000 +0000
@@ -19,8 +19,8 @@
     enum { LF = 0xA, CR = 0xD, NL = '\n' };
     enum { default_maxlen = 76 };
     enum { eq_sign = 100 };
-    static const char sEncTable[];
-    static const char sDecTable[];
+    static const signed char sEncTable[];
+    static const signed char sDecTable[];
     static const int sDecTableSz;
 public:
     class Encoder; class Decoder;
--- mimetic-0.9.8/mimetic/codec/base64.cxx.old	2014-06-17 08:12:00.000000000 +0000
+++ mimetic-0.9.8/mimetic/codec/base64.cxx	2018-08-01 05:36:23.010000000 +0000
@@ -8,12 +8,12 @@
 
 using namespace mimetic;
 
-const char Base64::sEncTable[] = 
+const signed char Base64::sEncTable[] = 
     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
     "abcdefghijklmnopqrstuvwxyz"
     "0123456789+/=";
 
-const char Base64::sDecTable[] = {
+const signed char Base64::sDecTable[] = {
         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
         -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
@@ -29,5 +29,5 @@
         49,50,51,-1
 };
 
-const int Base64::sDecTableSz = sizeof(Base64::sDecTable) / sizeof(char);
+const int Base64::sDecTableSz = sizeof(Base64::sDecTable) / sizeof(signed char);