diff --git a/apps/opencs/model/filter/parser.cpp b/apps/opencs/model/filter/parser.cpp
index d363b4849d..6f185d60fa 100644
--- a/apps/opencs/model/filter/parser.cpp
+++ b/apps/opencs/model/filter/parser.cpp
@@ -17,6 +17,19 @@
 #include "textnode.hpp"
 #include "valuenode.hpp"
 
+namespace
+{
+    bool isAlpha(char c)
+    {
+        return std::isalpha(static_cast<unsigned char>(c));
+    }
+
+    bool isDigit(char c)
+    {
+        return std::isdigit(static_cast<unsigned char>(c));
+    }
+}
+
 namespace CSMFilter
 {
     struct Token
@@ -103,7 +116,7 @@ CSMFilter::Token CSMFilter::Parser::getStringToken()
     {
         char c = mInput[mIndex];
 
-        if (std::isalpha (c) || c==':' || c=='_' || (!string.empty() && std::isdigit (c)) || c=='"' ||
+        if (isAlpha(c) || c==':' || c=='_' || (!string.empty() && isDigit(c)) || c=='"' ||
             (!string.empty() && string[0]=='"'))
             string += c;
         else
@@ -150,7 +163,7 @@ CSMFilter::Token CSMFilter::Parser::getNumberToken()
     {
         char c = mInput[mIndex];
 
-        if (std::isdigit (c))
+        if (isDigit(c))
         {
             string += c;
             hasDigit = true;
@@ -225,10 +238,10 @@ CSMFilter::Token CSMFilter::Parser::getNextToken()
         case '!': ++mIndex; return Token (Token::Type_OneShot);
     }
 
-    if (c=='"' || c=='_' || std::isalpha (c) || c==':')
+    if (c=='"' || c=='_' || isAlpha(c) || c==':')
         return getStringToken();
 
-    if (c=='-' || c=='.' || std::isdigit (c))
+    if (c=='-' || c=='.' || isDigit(c))
         return getNumberToken();
 
     error();
diff --git a/apps/openmw/mwinput/keyboardmanager.cpp b/apps/openmw/mwinput/keyboardmanager.cpp
index c5a665e5c6..b121b665e7 100644
--- a/apps/openmw/mwinput/keyboardmanager.cpp
+++ b/apps/openmw/mwinput/keyboardmanager.cpp
@@ -42,9 +42,9 @@ namespace MWInput
 
         bool consumed = SDL_IsTextInputActive() &&  // Little trick to check if key is printable
                         (!(SDLK_SCANCODE_MASK & arg.keysym.sym) &&
-                        (arg.keysym.sym >= 0 && arg.keysym.sym <= 255 && std::isprint(arg.keysym.sym) ||
                         // Don't trust isprint for symbols outside the extended ASCII range
-                        (kc == MyGUI::KeyCode::None && arg.keysym.sym > 0xff)));
+                        ((kc == MyGUI::KeyCode::None && arg.keysym.sym > 0xff) ||
+                        (arg.keysym.sym >= 0 && arg.keysym.sym <= 255 && std::isprint(arg.keysym.sym))));
         if (kc != MyGUI::KeyCode::None && !mBindingsManager->isDetectingBindingState())
         {
             if (MWBase::Environment::get().getWindowManager()->injectKeyPress(kc, 0, arg.repeat))
diff --git a/components/lua/configuration.cpp b/components/lua/configuration.cpp
index 4598ed2508..172d958029 100644
--- a/components/lua/configuration.cpp
+++ b/components/lua/configuration.cpp
@@ -30,6 +30,11 @@ namespace LuaUtil
             {"POTION", ESM::LuaScriptCfg::sPotion},
             {"WEAPON", ESM::LuaScriptCfg::sWeapon},
         };
+
+        bool isSpace(char c)
+        {
+            return std::isspace(static_cast<unsigned char>(c));
+        }
     }
 
     const std::vector<int> ScriptsConfiguration::sEmpty;
@@ -101,11 +106,11 @@ namespace LuaUtil
             if (!line.empty() && line.back() == '\r')
                 line = line.substr(0, line.size() - 1);
 
-            while (!line.empty() && std::isspace(line[0]))
+            while (!line.empty() && isSpace(line[0]))
                 line = line.substr(1);
             if (line.empty() || line[0] == '#')  // Skip empty lines and comments
                 continue;
-            while (!line.empty() && std::isspace(line.back()))
+            while (!line.empty() && isSpace(line.back()))
                 line = line.substr(0, line.size() - 1);
 
             if (!Misc::StringUtils::ciEndsWith(line, ".lua"))
@@ -118,7 +123,7 @@ namespace LuaUtil
                 throw std::runtime_error(Misc::StringUtils::format("No flags found in: %s", std::string(line)));
             std::string_view flagsStr = line.substr(0, semicolonPos);
             std::string_view scriptPath = line.substr(semicolonPos + 1);
-            while (std::isspace(scriptPath[0]))
+            while (isSpace(scriptPath[0]))
                 scriptPath = scriptPath.substr(1);
 
             // Parse flags
@@ -126,10 +131,10 @@ namespace LuaUtil
             size_t flagsPos = 0;
             while (true)
             {
-                while (flagsPos < flagsStr.size() && (std::isspace(flagsStr[flagsPos]) || flagsStr[flagsPos] == ','))
+                while (flagsPos < flagsStr.size() && (isSpace(flagsStr[flagsPos]) || flagsStr[flagsPos] == ','))
                     flagsPos++;
                 size_t startPos = flagsPos;
-                while (flagsPos < flagsStr.size() && !std::isspace(flagsStr[flagsPos]) && flagsStr[flagsPos] != ',')
+                while (flagsPos < flagsStr.size() && !isSpace(flagsStr[flagsPos]) && flagsStr[flagsPos] != ',')
                     flagsPos++;
                 if (startPos == flagsPos)
                     break;
diff --git a/components/misc/stringops.hpp b/components/misc/stringops.hpp
index c8d236a9d0..fe4be00006 100644
--- a/components/misc/stringops.hpp
+++ b/components/misc/stringops.hpp
@@ -187,7 +187,7 @@ public:
         const auto notSpace = [](char ch)
         {
             // TODO Do we care about multibyte whitespace?
-            return !std::isspace(ch);
+            return !std::isspace(static_cast<unsigned char>(ch));
         };
         // left trim
         s.erase(s.begin(), std::find_if(s.begin(), s.end(), notSpace));
diff --git a/components/settings/parser.cpp b/components/settings/parser.cpp
index f2419dfdd6..8d387ab9c7 100644
--- a/components/settings/parser.cpp
+++ b/components/settings/parser.cpp
@@ -311,7 +311,7 @@ void Settings::SettingsFileParser::saveSettingsFile(const std::string& file, con
 
 bool Settings::SettingsFileParser::skipWhiteSpace(size_t& i, std::string& str)
 {
-    while (i < str.size() && std::isspace(str[i], std::locale::classic()))
+    while (i < str.size() && std::isspace(static_cast<unsigned char>(str[i]), std::locale::classic()))
     {
         ++i;
     }