diff --git a/AK/URLParser.cpp b/AK/URLParser.cpp
index f50c2bcb3a7..5479e7951fb 100644
--- a/AK/URLParser.cpp
+++ b/AK/URLParser.cpp
@@ -177,7 +177,8 @@ URL URLParser::parse(Badge<URL>, StringView const& raw_input, URL const* base_ur
     size_t start_index = 0;
     size_t end_index = raw_input.length();
     for (size_t i = 0; i < raw_input.length(); ++i) {
-        if (0 <= raw_input[i] && raw_input[i] <= 0x20) {
+        i8 ch = raw_input[i];
+        if (0 <= ch && ch <= 0x20) {
             ++start_index;
             has_validation_error = true;
         } else {
@@ -185,7 +186,8 @@ URL URLParser::parse(Badge<URL>, StringView const& raw_input, URL const* base_ur
         }
     }
     for (ssize_t i = raw_input.length() - 1; i >= 0; --i) {
-        if (0 <= raw_input[i] && raw_input[i] <= 0x20) {
+        i8 ch = raw_input[i];
+        if (0 <= ch && ch <= 0x20) {
             --end_index;
             has_validation_error = true;
         } else {
diff --git a/Userland/Libraries/LibJS/Lexer.cpp b/Userland/Libraries/LibJS/Lexer.cpp
index 386fdef2bf8..32034fa8310 100644
--- a/Userland/Libraries/LibJS/Lexer.cpp
+++ b/Userland/Libraries/LibJS/Lexer.cpp
@@ -139,9 +139,10 @@ void Lexer::consume()
     auto did_reach_eof = [this] {
         if (m_position != m_source.length())
             return false;
+        m_eof = true;
+        m_current_char = '\0';
         m_position++;
         m_line_column++;
-        m_current_char = EOF;
         return true;
     };
 
@@ -276,7 +277,7 @@ bool Lexer::match(char a, char b, char c, char d) const
 
 bool Lexer::is_eof() const
 {
-    return m_current_char == EOF;
+    return m_eof;
 }
 
 bool Lexer::is_line_terminator() const
@@ -540,7 +541,7 @@ Token Lexer::next()
         } else {
             consume();
         }
-    } else if (m_current_char == EOF) {
+    } else if (m_eof) {
         if (unterminated_comment) {
             token_type = TokenType::Invalid;
             token_message = "Unterminated multi-line comment";
diff --git a/Userland/Libraries/LibJS/Lexer.h b/Userland/Libraries/LibJS/Lexer.h
index 7541ff7fce6..616014499a8 100644
--- a/Userland/Libraries/LibJS/Lexer.h
+++ b/Userland/Libraries/LibJS/Lexer.h
@@ -46,6 +46,7 @@ private:
     size_t m_position { 0 };
     Token m_current_token;
     char m_current_char { 0 };
+    bool m_eof { false };
 
     StringView m_filename;
     size_t m_line_number { 1 };
diff --git a/Userland/Libraries/LibJS/Runtime/DateConstructor.cpp b/Userland/Libraries/LibJS/Runtime/DateConstructor.cpp
index ac2865df9b0..981a640f0f7 100644
--- a/Userland/Libraries/LibJS/Runtime/DateConstructor.cpp
+++ b/Userland/Libraries/LibJS/Runtime/DateConstructor.cpp
@@ -40,7 +40,7 @@ static Value parse_simplified_iso8601(const String& iso_8601)
 
     int year = -1, month = -1, day = -1;
     int hours = -1, minutes = -1, seconds = -1, milliseconds = -1;
-    char timezone = -1;
+    int timezone = -1;
     int timezone_hours = -1, timezone_minutes = -1;
     auto lex_year = [&]() {
         if (lexer.consume_specific('+'))
diff --git a/Userland/Libraries/LibRegex/RegexLexer.cpp b/Userland/Libraries/LibRegex/RegexLexer.cpp
index f22778c0f28..daaa6658512 100644
--- a/Userland/Libraries/LibRegex/RegexLexer.cpp
+++ b/Userland/Libraries/LibRegex/RegexLexer.cpp
@@ -36,11 +36,11 @@ Lexer::Lexer(const StringView source)
 {
 }
 
-ALWAYS_INLINE char Lexer::peek(size_t offset) const
+ALWAYS_INLINE int Lexer::peek(size_t offset) const
 {
     if ((m_position + offset) >= m_source.length())
         return EOF;
-    return m_source[m_position + offset];
+    return (unsigned char)m_source[m_position + offset];
 }
 
 void Lexer::back(size_t offset)
@@ -90,6 +90,7 @@ char Lexer::skip()
 {
     auto c = peek();
     consume();
+    VERIFY(c != EOF);
     return c;
 }
 
diff --git a/Userland/Libraries/LibRegex/RegexLexer.h b/Userland/Libraries/LibRegex/RegexLexer.h
index 5a5d200e679..c196d94432b 100644
--- a/Userland/Libraries/LibRegex/RegexLexer.h
+++ b/Userland/Libraries/LibRegex/RegexLexer.h
@@ -76,7 +76,7 @@ public:
     const auto& source() const { return m_source; }
 
 private:
-    ALWAYS_INLINE char peek(size_t offset = 0) const;
+    ALWAYS_INLINE int peek(size_t offset = 0) const;
     ALWAYS_INLINE void consume();
 
     StringView m_source {};
diff --git a/Userland/Libraries/LibSQL/Lexer.cpp b/Userland/Libraries/LibSQL/Lexer.cpp
index 4431bbd340f..50598b3159b 100644
--- a/Userland/Libraries/LibSQL/Lexer.cpp
+++ b/Userland/Libraries/LibSQL/Lexer.cpp
@@ -121,7 +121,8 @@ void Lexer::consume()
     auto did_reach_eof = [this] {
         if (m_position != m_source.length())
             return false;
-        m_current_char = EOF;
+        m_eof = true;
+        m_current_char = '\0';
         ++m_line_column;
         ++m_position;
         return true;
@@ -325,7 +326,7 @@ bool Lexer::is_line_break() const
 
 bool Lexer::is_eof() const
 {
-    return m_current_char == EOF;
+    return m_eof;
 }
 
 }
diff --git a/Userland/Libraries/LibSQL/Lexer.h b/Userland/Libraries/LibSQL/Lexer.h
index 89faf4f2e41..2ec93a2e803 100644
--- a/Userland/Libraries/LibSQL/Lexer.h
+++ b/Userland/Libraries/LibSQL/Lexer.h
@@ -50,6 +50,7 @@ private:
     size_t m_line_number { 1 };
     size_t m_line_column { 0 };
     char m_current_char { 0 };
+    bool m_eof { false };
     size_t m_position { 0 };
 };
 
diff --git a/Userland/Shell/AST.h b/Userland/Shell/AST.h
index a35f546ec61..b5efc220047 100644
--- a/Userland/Shell/AST.h
+++ b/Userland/Shell/AST.h
@@ -388,7 +388,7 @@ public:
     }
 
 private:
-    char m_name { -1 };
+    char m_name { 0 };
 };
 
 class TildeValue final : public Value {
@@ -1290,7 +1290,7 @@ private:
     virtual Vector<Line::CompletionSuggestion> complete_for_editor(Shell&, size_t, const HitTestResult&) override;
     virtual HitTestResult hit_test_position(size_t) const override;
 
-    char m_name { -1 };
+    char m_name { 0 };
 };
 
 class Juxtaposition final : public Node {