diff --git a/konversation/src/blowfish/b64stuff.cpp b/konversation/src/blowfish/b64stuff.cpp
index 72f0776..96782ac 100644
--- a/konversation/src/blowfish/b64stuff.cpp
+++ b/konversation/src/blowfish/b64stuff.cpp
@@ -100,7 +100,7 @@ unsigned char *spc_base64_encode(unsigned char *input, size_t len, int wrap) {
 
 
 //---------------------------------------------------------------------------
-static char b64revtb[256] = {
+static signed char b64revtb[256] = {
   -3, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*0-15*/
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*16-31*/
   -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /*32-47*/