diff --git a/include/upa/idna/bitmask_operators.hpp b/include/upa/idna/bitmask_operators.hpp
index 0151e23..17ed3e8 100644
--- a/include/upa/idna/bitmask_operators.hpp
+++ b/include/upa/idna/bitmask_operators.hpp
@@ -33,7 +33,13 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
-#include<type_traits>
+#include "config.h"
+
+#ifndef UPA_MODULE
+# include<type_traits>
+#endif // UPA_MODULE
+
+UPA_EXPORT_BEGIN
 
 namespace upa::idna {
 
@@ -104,4 +110,6 @@ operator^=(E& lhs, E rhs) noexcept {
     return lhs;
 }
 
+UPA_EXPORT_END
+
 #endif // UPA_IDNA_BITMASK_OPERATORS_HPP
diff --git a/include/upa/idna/config.h b/include/upa/idna/config.h
index eaf3106..bdf7b7c 100644
--- a/include/upa/idna/config.h
+++ b/include/upa/idna/config.h
@@ -31,4 +31,12 @@
 # define UPA_IDNA_API
 #endif
 
+// The following macros have values when the library is compiled as a module
+
+#ifndef UPA_EXPORT
+# define UPA_EXPORT
+# define UPA_EXPORT_BEGIN
+# define UPA_EXPORT_END
+#endif
+
 #endif // UPA_IDNA_CONFIG_H
diff --git a/include/upa/idna/idna.h b/include/upa/idna/idna.h
index 9cb240c..89804f1 100644
--- a/include/upa/idna/idna.h
+++ b/include/upa/idna/idna.h
@@ -1,4 +1,4 @@
-// Copyright 2017-2025 Rimas Misevičius
+// Copyright 2017-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
@@ -8,10 +8,15 @@
 #include "bitmask_operators.hpp"
 #include "config.h" // IWYU pragma: export
 #include "idna_version.h" // IWYU pragma: export
-#include <string>
+
+#ifndef UPA_MODULE
+# include <string>
+#endif // UPA_MODULE
 
 namespace upa::idna {
 
+UPA_EXPORT_BEGIN
+
 enum class Option {
     Default           = 0,
     UseSTD3ASCIIRules = 0x0001,
@@ -27,6 +32,7 @@ enum class Option {
 template<>
 struct enable_bitmask_operators<Option> : public std::true_type {};
 
+UPA_EXPORT_END
 
 namespace detail {
 
@@ -64,6 +70,7 @@ UPA_IDNA_API bool to_unicode_mapped(std::u32string& domain, const std::u32string
 
 } // namespace detail
 
+UPA_EXPORT_BEGIN
 
 /// @brief Implements the Unicode IDNA ToASCII
 ///
@@ -166,6 +173,7 @@ inline bool domain_to_unicode(std::u32string& domain, const CharT* input, const
     return make_unicode_version(17);
 }
 
+UPA_EXPORT_END
 
 } // namespace upa::idna
 
diff --git a/include/upa/idna/nfc.h b/include/upa/idna/nfc.h
index cfbce7b..b20911e 100644
--- a/include/upa/idna/nfc.h
+++ b/include/upa/idna/nfc.h
@@ -1,4 +1,4 @@
-// Copyright 2024-2025 Rimas Misevičius
+// Copyright 2024-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
@@ -6,7 +6,10 @@
 #define UPA_IDNA_NFC_H
 
 #include "config.h" // IWYU pragma: export
-#include <string>
+
+#ifndef UPA_MODULE
+# include <string>
+#endif // UPA_MODULE
 
 namespace upa::idna {
 
diff --git a/include/upa/idna/punycode.h b/include/upa/idna/punycode.h
index ff2d6e5..b25eb42 100644
--- a/include/upa/idna/punycode.h
+++ b/include/upa/idna/punycode.h
@@ -1,4 +1,4 @@
-// Copyright 2017-2025 Rimas Misevičius
+// Copyright 2017-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
@@ -6,7 +6,10 @@
 #define UPA_IDNA_PUNYCODE_H
 
 #include "config.h" // IWYU pragma: export
-#include <string>
+
+#ifndef UPA_MODULE
+# include <string>
+#endif
 
 namespace upa::idna::punycode {
 
diff --git a/src/idna.cpp b/src/idna.cpp
index 721098d..c84a055 100644
--- a/src/idna.cpp
+++ b/src/idna.cpp
@@ -2,17 +2,19 @@
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
-#include "upa/idna/idna.h"
+#ifndef UPA_MODULE
+# include "upa/idna/idna.h"
+# include "upa/idna/nfc.h"
+# include "upa/idna/punycode.h"
+# include <algorithm>
+# include <iterator>
+# include <stdexcept>
+# include <string>
+# include <type_traits> // std::make_unsigned
+#endif // UPA_MODULE
+
 #include "idna_table.h"
 #include "iterate_utf.h"
-#include "upa/idna/nfc.h"
-#include "upa/idna/punycode.h"
-
-#include <algorithm>
-#include <iterator>
-#include <stdexcept>
-#include <string>
-#include <type_traits> // std::make_unsigned
 
 namespace upa::idna {
 namespace {
diff --git a/src/idna_table.h b/src/idna_table.h
index 12b5fa0..794438f 100644
--- a/src/idna_table.h
+++ b/src/idna_table.h
@@ -5,8 +5,10 @@
 #ifndef UPA_IDNA_IDNA_TABLE_H
 #define UPA_IDNA_IDNA_TABLE_H
 
-#include <cstddef>
-#include <cstdint>
+#ifndef UPA_MODULE
+# include <cstddef>
+# include <cstdint>
+#endif // UPA_MODULE
 
 namespace upa::idna::util {
 
diff --git a/src/iterate_utf.h b/src/iterate_utf.h
index 0aaa2f9..656b079 100644
--- a/src/iterate_utf.h
+++ b/src/iterate_utf.h
@@ -5,7 +5,9 @@
 #ifndef UPA_IDNA_ITERATE_UTF_H
 #define UPA_IDNA_ITERATE_UTF_H
 
-#include <cstdint>
+#ifndef UPA_MODULE
+# include <cstdint>
+#endif // UPA_MODULE
 
 namespace upa::idna::util {
 
diff --git a/src/nfc.cpp b/src/nfc.cpp
index afff90d..3418622 100644
--- a/src/nfc.cpp
+++ b/src/nfc.cpp
@@ -1,12 +1,14 @@
-// Copyright 2024-2025 Rimas Misevičius
+// Copyright 2024-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
-#include "upa/idna/nfc.h"
-#include "nfc_table.h"
-#include <algorithm>
-#include <utility> // std::move
+#ifndef UPA_MODULE
+# include "upa/idna/nfc.h"
+# include <algorithm>
+# include <utility> // std::move
+#endif // UPA_MODULE
 
+#include "nfc_table.h"
 
 namespace upa::idna {
 
diff --git a/src/nfc_table.h b/src/nfc_table.h
index 4e5ba1d..2c1e9df 100644
--- a/src/nfc_table.h
+++ b/src/nfc_table.h
@@ -1,12 +1,14 @@
-// Copyright 2024-2025 Rimas Misevičius
+// Copyright 2024-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
 #ifndef UPA_IDNA_NFC_TABLE_H
 #define UPA_IDNA_NFC_TABLE_H
 
-#include <cstddef>
-#include <cstdint>
+#ifndef UPA_MODULE
+# include <cstddef>
+# include <cstdint>
+#endif // UPA_MODULE
 
 namespace upa::idna::normalize {
 
diff --git a/src/punycode.cpp b/src/punycode.cpp
index b744e11..947727c 100644
--- a/src/punycode.cpp
+++ b/src/punycode.cpp
@@ -1,11 +1,13 @@
-// Copyright 2017-2024 Rimas Misevičius
+// Copyright 2017-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
-#include "upa/idna/punycode.h"
-#include <algorithm>
-#include <cstdint>
-#include <type_traits>
+#ifndef UPA_MODULE
+# include "upa/idna/punycode.h"
+# include <algorithm>
+# include <cstdint>
+# include <type_traits>
+#endif // UPA_MODULE
 
 namespace upa::idna::punycode {
 
diff --git a/tools/amalgamate/config-cpp.prologue b/tools/amalgamate/config-cpp.prologue
index 2029287..b5d0fab 100644
--- a/tools/amalgamate/config-cpp.prologue
+++ b/tools/amalgamate/config-cpp.prologue
@@ -1,6 +1,8 @@
-// Copyright 2017-2025 Rimas Misevičius
+// Copyright 2017-2026 Rimas Misevičius
 // Distributed under the BSD-style license that can be
 // found in the LICENSE file.
 //
-#include "upa/idna.h"
+#ifndef UPA_MODULE
+# include "upa/idna.h"
+#endif // UPA_MODULE