diff --git a/src/lib/AST/ParseJavadoc.cpp b/src/lib/AST/ParseJavadoc.cpp
index a12346a1e..d4d88702f 100644
--- a/src/lib/AST/ParseJavadoc.cpp
+++ b/src/lib/AST/ParseJavadoc.cpp
@@ -7,6 +7,7 @@
 // Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com)
 // Copyright (c) 2023 Krystian Stasiowski (sdkrystian@gmail.com)
 // Copyright (c) 2024 Alan de Freitas (alandefreitas@gmail.com)
+// Copyright (c) 2025 Gennaro Prota (gennaro.prota@gmail.com)
 //
 // Official repository: https://github.com/cppalliance/mrdocs
 //
@@ -539,7 +540,7 @@ parseStyled(StringRef s)
         }
     };
 
-    auto isPunctuationOrSpace = [](char c) {
+    auto isPunctuationOrSpace = [](unsigned char c) {
         return std::isspace(c) || std::ispunct(c);
     };
 
diff --git a/src/lib/Support/Validate.cpp b/src/lib/Support/Validate.cpp
index 1ae7cafd4..c910e97e4 100644
--- a/src/lib/Support/Validate.cpp
+++ b/src/lib/Support/Validate.cpp
@@ -4,6 +4,7 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 // Copyright (c) 2023 Vinnie Falco (vinnie.falco@gmail.com)
+// Copyright (c) 2025 Gennaro Prota (gennaro.prota@gmail.com)
 //
 // Official repository: https://github.com/cppalliance/mrdocs
 //
@@ -29,7 +30,7 @@ validAdocSectionID(
     return
         s[0] == '_' ||
         s[0] == ':' ||
-        std::isalpha(s[0]);
+        std::isalpha(static_cast<unsigned char>(s[0]));
 }
 
 } // mrdocs