diff --git a/src/epsimage.cpp b/src/epsimage.cpp
index 9db942f7..4c1d30d9 100644
--- a/src/epsimage.cpp
+++ b/src/epsimage.cpp
@@ -29,7 +29,7 @@
 // *****************************************************************************
 namespace {
 using namespace Exiv2;
-using Exiv2::byte;
+using namespace Exiv2::Internal;
 
 // signature of DOS EPS
 constexpr auto dosEpsSignature = std::string_view("\xC5\xD0\xD3\xC6");
diff --git a/src/utils.cpp b/src/utils.cpp
index 57e9fa9d..111aff00 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -4,7 +4,7 @@
 #include <cctype>
 #include <iterator>
 
-namespace Exiv2 {
+namespace Exiv2::Internal {
 
 std::string upper(const std::string& str) {
   std::string result;
@@ -18,4 +18,4 @@ std::string lower(const std::string& a) {
   return b;
 }
 
-}  // namespace Exiv2
+}  // namespace Exiv2::Internal
diff --git a/src/utils.hpp b/src/utils.hpp
index a8f21c43..1e16648d 100644
--- a/src/utils.hpp
+++ b/src/utils.hpp
@@ -4,7 +4,8 @@
 #include <string>
 #include <string_view>
 
-namespace Exiv2 {
+namespace Exiv2::Internal {
+
 constexpr bool startsWith(std::string_view s, std::string_view start) {
   return s.find(start) == 0;
 }
@@ -15,6 +16,6 @@ std::string upper(const std::string& str);
 /// @brief Returns the lowercase version of \b str
 std::string lower(const std::string& str);
 
-}  // namespace Exiv2
+}  // namespace Exiv2::Internal
 
 #endif  // EXIV2_UTILS_HPP
diff --git a/src/xmpsidecar.cpp b/src/xmpsidecar.cpp
index 53485c10..ecb95027 100644
--- a/src/xmpsidecar.cpp
+++ b/src/xmpsidecar.cpp
@@ -84,7 +84,7 @@ void XmpSidecar::readMetadata() {
 }  // XmpSidecar::readMetadata
 
 static bool matchi(const std::string& key, const char* substr) {
-  return lower(key).find(substr) != std::string::npos;
+  return Internal::lower(key).find(substr) != std::string::npos;
 }
 
 void XmpSidecar::writeMetadata() {
diff --git a/unitTests/test_utils.cpp b/unitTests/test_utils.cpp
index 2b39b005..f94638e3 100644
--- a/unitTests/test_utils.cpp
+++ b/unitTests/test_utils.cpp
@@ -4,7 +4,7 @@
 
 #include <gtest/gtest.h>
 
-using namespace Exiv2;
+using namespace Exiv2::Internal;
 
 TEST(stringUtils, startsWithReturnsTrue) {
   ASSERT_TRUE(startsWith("Exiv2 rocks", "Exiv2"));