diff --git a/src/actions/transformations/css_decode.cc b/src/actions/transformations/css_decode.cc
index c5de63f73..41da9390e 100644
--- a/src/actions/transformations/css_decode.cc
+++ b/src/actions/transformations/css_decode.cc
@@ -17,6 +17,7 @@
 
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
 
 namespace modsecurity::actions::transformations {
 
diff --git a/src/actions/transformations/escape_seq_decode.cc b/src/actions/transformations/escape_seq_decode.cc
index 2cc413e71..94df2269d 100644
--- a/src/actions/transformations/escape_seq_decode.cc
+++ b/src/actions/transformations/escape_seq_decode.cc
@@ -17,6 +17,8 @@
 
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
+
 namespace modsecurity::actions::transformations {
 
 
diff --git a/src/actions/transformations/html_entity_decode.cc b/src/actions/transformations/html_entity_decode.cc
index 0b9d811b3..8a0cc3e97 100644
--- a/src/actions/transformations/html_entity_decode.cc
+++ b/src/actions/transformations/html_entity_decode.cc
@@ -23,6 +23,7 @@
 #include "src/compat/msvc.h"
 #endif
 
+using namespace modsecurity::utils::string;
 
 namespace modsecurity::actions::transformations {
 
diff --git a/src/actions/transformations/js_decode.cc b/src/actions/transformations/js_decode.cc
index 394a2cdcf..857125c74 100644
--- a/src/actions/transformations/js_decode.cc
+++ b/src/actions/transformations/js_decode.cc
@@ -17,6 +17,7 @@
 
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
 
 namespace modsecurity::actions::transformations {
 
diff --git a/src/actions/transformations/sql_hex_decode.cc b/src/actions/transformations/sql_hex_decode.cc
index 8f19e6197..0ce240872 100644
--- a/src/actions/transformations/sql_hex_decode.cc
+++ b/src/actions/transformations/sql_hex_decode.cc
@@ -19,6 +19,7 @@
 
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
 
 namespace modsecurity::actions::transformations {
 
diff --git a/src/actions/transformations/url_decode_uni.cc b/src/actions/transformations/url_decode_uni.cc
index 57df7a566..58d683c85 100644
--- a/src/actions/transformations/url_decode_uni.cc
+++ b/src/actions/transformations/url_decode_uni.cc
@@ -18,6 +18,7 @@
 #include "modsecurity/rules_set.h"
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
 
 namespace modsecurity::actions::transformations {
 
diff --git a/src/utils/decode.cc b/src/utils/decode.cc
index 32d95301e..2735cf3ee 100644
--- a/src/utils/decode.cc
+++ b/src/utils/decode.cc
@@ -17,9 +17,9 @@
 #include "modsecurity/modsecurity.h"
 #include "src/utils/string.h"
 
+using namespace modsecurity::utils::string;
 
-namespace modsecurity {
-namespace utils {
+namespace modsecurity::utils {
 
 
 bool urldecode_nonstrict_inplace(std::string &val,
@@ -112,5 +112,4 @@ std::string uri_decode(const std::string & sSrc) {
 }
 
 
-}  // namespace utils
-}  // namespace modsecurity
+}  // namespace modsecurity::utils
diff --git a/src/utils/string.h b/src/utils/string.h
index dbfb9b479..f5e52ff06 100644
--- a/src/utils/string.h
+++ b/src/utils/string.h
@@ -13,6 +13,9 @@
  *
  */
 
+#ifndef SRC_UTILS_STRING_H_
+#define SRC_UTILS_STRING_H_
+
 #include <ctime>
 #include <string>
 #include <cstring>
@@ -27,18 +30,21 @@
 #include "src/compat/msvc.h"
 #endif
 
-#ifndef SRC_UTILS_STRING_H_
-#define SRC_UTILS_STRING_H_
+namespace modsecurity::utils::string {
 
-#define VALID_HEX(X) (((X >= '0') && (X <= '9')) || \
-    ((X >= 'a') && (X <= 'f')) || ((X >= 'A') && (X <= 'F')))
-#define ISODIGIT(X) ((X >= '0') && (X <= '7'))
-#define NBSP 160
+template<typename CharT>
+constexpr bool VALID_HEX(CharT X) {
+    return ((X >= '0') && (X <= '9')) 
+        || ((X >= 'a') && (X <= 'f'))
+        || ((X >= 'A') && (X <= 'F'));
+}
 
+template<typename CharT>
+constexpr bool ISODIGIT(CharT X) {
+    return (X >= '0') && (X <= '7');
+}
 
-namespace modsecurity {
-namespace utils {
-namespace string {
+constexpr unsigned char NBSP = 160;
 
 const char HEX2DEC[256] = {
     /*       0  1  2  3   4  5  6  7   8  9  A  B   C  D  E  F */
@@ -271,8 +277,6 @@ inline std::string toupper(std::string str) { // cppcheck-suppress passedByValue
 }
 
 
-}  // namespace string
-}  // namespace utils
-}  // namespace modsecurity
+}  // namespace modsecurity::utils::string
 
 #endif  // SRC_UTILS_STRING_H_