diff --git a/lib/dec/head.c b/lib/dec/head.c
index 08cbb37a..f19b7958 100644
--- a/lib/dec/head.c
+++ b/lib/dec/head.c
@@ -1,6 +1,6 @@
 int ret = 0;
-const char *c = src;
-char *o = out;
+const unsigned char *c = (const unsigned char *)src;
+unsigned char *o = (unsigned char *)out;
 unsigned char q;
 
 /* Use local temporaries to avoid cache thrashing: */
diff --git a/lib/dec/tail.c b/lib/dec/tail.c
index efdfd482..f59fa7d9 100644
--- a/lib/dec/tail.c
+++ b/lib/dec/tail.c
@@ -2,7 +2,7 @@
 			ret = 1;
 			break;
 		}
-		if ((q = base64_table_dec[(unsigned char)*c++]) >= 254) {
+		if ((q = base64_table_dec[*c++]) >= 254) {
 			st.eof = 1;
 			/* Treat character '=' as invalid for byte 0: */
 			break;
@@ -14,7 +14,7 @@
 			ret = 1;
 			break;
 		}
-		if ((q = base64_table_dec[(unsigned char)*c++]) >= 254) {
+		if ((q = base64_table_dec[*c++]) >= 254) {
 			st.eof = 1;
 			/* Treat character '=' as invalid for byte 1: */
 			break;
@@ -28,7 +28,7 @@
 			ret = 1;
 			break;
 		}
-		if ((q = base64_table_dec[(unsigned char)*c++]) >= 254) {
+		if ((q = base64_table_dec[*c++]) >= 254) {
 			st.eof = 1;
 			/* When q == 254, the input char is '='. Return 1 and EOF.
 			 * Technically, should check if next byte is also '=', but never mind.
@@ -45,7 +45,7 @@
 			ret = 1;
 			break;
 		}
-		if ((q = base64_table_dec[(unsigned char)*c++]) >= 254) {
+		if ((q = base64_table_dec[*c++]) >= 254) {
 			st.eof = 1;
 			/* When q == 254, the input char is '='. Return 1 and EOF.
 			 * When q == 255, the input char is invalid. Return 0 and EOF. */
diff --git a/lib/enc/head.c b/lib/enc/head.c
index f586822d..36dda07d 100644
--- a/lib/enc/head.c
+++ b/lib/enc/head.c
@@ -1,7 +1,7 @@
 /* Assume that *out is large enough to contain the output.
  * Theoretically it should be 4/3 the length of src. */
-const unsigned char *c = (unsigned char *)src;
-char *o = out;
+const unsigned char *c = (const unsigned char *)src;
+unsigned char *o = (unsigned char *)out;
 
 /* Use local temporaries to avoid cache thrashing: */
 size_t outl = 0;