diff --git a/src/lib/dns/name.cc b/src/lib/dns/name.cc
index ff003744a7..7d34a09e6f 100644
--- a/src/lib/dns/name.cc
+++ b/src/lib/dns/name.cc
@@ -54,7 +54,7 @@ namespace {
 /// improve the performance of message rendering (which internally uses the
 /// array heavily) about 27%.  Since we want to achieve very good performance
 /// for message rendering in some cases, we'll keep using it.
-const char digitvalue[256] = {
+const signed char digitvalue[256] = {
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 16
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 32
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 48
diff --git a/src/lib/util/encode/binary_from_base16.h b/src/lib/util/encode/binary_from_base16.h
index e9fdd277b1..307842a83b 100644
--- a/src/lib/util/encode/binary_from_base16.h
+++ b/src/lib/util/encode/binary_from_base16.h
@@ -36,7 +36,7 @@ template<class CharType>
 struct to_4_bit {
     typedef CharType result_type;
     CharType operator()(CharType t) const{
-        const char lookup_table[] = {
+        const signed char lookup_table[] = {
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 00-0f
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 10-1f
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 20-2f
diff --git a/src/lib/util/encode/binary_from_base32hex.h b/src/lib/util/encode/binary_from_base32hex.h
index 43b7d64dda..457fa3ca75 100644
--- a/src/lib/util/encode/binary_from_base32hex.h
+++ b/src/lib/util/encode/binary_from_base32hex.h
@@ -38,7 +38,7 @@ template<class CharType>
 struct to_5_bit {
     typedef CharType result_type;
     CharType operator()(CharType t) const{
-        const char lookup_table[] = {
+        const signed char lookup_table[] = {
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 00-0f
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 10-1f
             -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 20-2f