diff --git a/bazel/cc_toolchains/clang_cc_toolchain_config.bzl b/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
index ec7e2220206f..e971a24d6f63 100644
--- a/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
+++ b/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
@@ -141,7 +141,8 @@ def _impl(ctx):
                             "-Wself-assign",
                             "-Wimplicit-fallthrough",
                             "-Wctad-maybe-unsupported",
-                            "-Wdelete-non-virtual-dtor",
+                            "-Wextra-semi",
+                            "-Wzero-as-null-pointer-constant",
                             # Don't warn on external code as we can't
                             # necessarily patch it easily. Note that these have
                             # to be initial directories in the `#include` line.
diff --git a/common/struct_reflection.h b/common/struct_reflection.h
index 9bb113819817..9221a939dc2d 100644
--- a/common/struct_reflection.h
+++ b/common/struct_reflection.h
@@ -72,7 +72,7 @@ constexpr auto CanListInitialize(...) -> bool {
 // 2) Add more AnyField<T>s until we can't initialize any more.
 template <typename T, bool AnyWorkedSoFar = false, typename... Fields>
 constexpr auto CountFields() -> int {
-  if constexpr (CanListInitialize<T, Fields...>(0)) {
+  if constexpr (CanListInitialize<T, Fields...>(nullptr)) {
     return CountFields<T, true, Fields..., AnyField<T>>();
   } else if constexpr (AnyWorkedSoFar) {
     constexpr int NumFields = sizeof...(Fields) - 1;
diff --git a/explorer/ast/bindings.cpp b/explorer/ast/bindings.cpp
index 27ce42a9915e..827b7a3e1223 100644
--- a/explorer/ast/bindings.cpp
+++ b/explorer/ast/bindings.cpp
@@ -63,7 +63,7 @@ void Bindings::Print(llvm::raw_ostream& out) const {
     out << sep << "`" << *binding << "`: `" << *value << "`";
   }
   out << "]";
-};
+}
 
 auto Bindings::None() -> Nonnull<const Bindings*> {
   static Nonnull<const Bindings*> bindings = new Bindings;
diff --git a/explorer/ast/statement.h b/explorer/ast/statement.h
index 2b7782ab3d26..e90504380205 100644
--- a/explorer/ast/statement.h
+++ b/explorer/ast/statement.h
@@ -264,7 +264,7 @@ class VariableDefinition : public Statement {
     return expression_category_;
   }
 
-  auto is_returned() const -> bool { return def_type_ == Returned; };
+  auto is_returned() const -> bool { return def_type_ == Returned; }
 
  private:
   Nonnull<Pattern*> pattern_;
diff --git a/explorer/file_test.cpp b/explorer/file_test.cpp
index 026ab47b5d65..89f60d63c03a 100644
--- a/explorer/file_test.cpp
+++ b/explorer/file_test.cpp
@@ -108,6 +108,6 @@ class ExplorerFileTest : public FileTestBase {
 
 }  // namespace
 
-CARBON_FILE_TEST_FACTORY(ExplorerFileTest);
+CARBON_FILE_TEST_FACTORY(ExplorerFileTest)
 
 }  // namespace Carbon::Testing
diff --git a/explorer/interpreter/heap.h b/explorer/interpreter/heap.h
index d1e25c540d70..15aee93ca97f 100644
--- a/explorer/interpreter/heap.h
+++ b/explorer/interpreter/heap.h
@@ -30,7 +30,7 @@ class Heap : public HeapAllocationInterface, public Printable<Heap> {
 
   // Constructs an empty Heap.
   explicit Heap(Nonnull<TraceStream*> trace_stream, Nonnull<Arena*> arena)
-      : arena_(arena), trace_stream_(trace_stream){};
+      : arena_(arena), trace_stream_(trace_stream) {}
 
   Heap(const Heap&) = delete;
   auto operator=(const Heap&) -> Heap& = delete;
diff --git a/explorer/syntax/BUILD b/explorer/syntax/BUILD
index f71c69654cea..226d0356d257 100644
--- a/explorer/syntax/BUILD
+++ b/explorer/syntax/BUILD
@@ -88,6 +88,7 @@ cc_library(
         "-Wno-unused-but-set-variable",
         "-Wno-unused-function",
         "-Wno-writable-strings",
+        "-Wno-zero-as-null-pointer-constant",
     ],
     # Running clang-tidy is slow, and explorer is currently feature frozen, so
     # don't spend time linting it.
diff --git a/explorer/syntax/lex_scan_helper.h b/explorer/syntax/lex_scan_helper.h
index 8c7b4f597089..3f707cd6d2f4 100644
--- a/explorer/syntax/lex_scan_helper.h
+++ b/explorer/syntax/lex_scan_helper.h
@@ -24,11 +24,11 @@ class StringLexHelper {
   // EOF.
   auto Advance() -> bool;
   // Returns the last scanned char.
-  auto last_char() -> char { return str_.back(); };
+  auto last_char() -> char { return str_.back(); }
   // Returns the scanned string.
-  auto str() -> const std::string& { return str_; };
+  auto str() -> const std::string& { return str_; }
 
-  auto is_eof() -> bool { return is_eof_; };
+  auto is_eof() -> bool { return is_eof_; }
 
  private:
   std::string str_;
diff --git a/language_server/language_server.cpp b/language_server/language_server.cpp
index fb35ef5dc332..9afc6f745a59 100644
--- a/language_server/language_server.cpp
+++ b/language_server/language_server.cpp
@@ -35,7 +35,7 @@ void LanguageServer::OnInitialize(
 
   llvm::json::Object reply{{"capabilities", std::move(capabilities)}};
   cb(reply);
-};
+}
 
 auto LanguageServer::onNotify(llvm::StringRef method, llvm::json::Value value)
     -> bool {
diff --git a/testing/file_test/file_test_base_test.cpp b/testing/file_test/file_test_base_test.cpp
index e395713bf784..b80ac8e6ca8c 100644
--- a/testing/file_test/file_test_base_test.cpp
+++ b/testing/file_test/file_test_base_test.cpp
@@ -162,6 +162,6 @@ class FileTestBaseTest : public FileTestBase {
 
 }  // namespace
 
-CARBON_FILE_TEST_FACTORY(FileTestBaseTest);
+CARBON_FILE_TEST_FACTORY(FileTestBaseTest)
 
 }  // namespace Carbon::Testing
diff --git a/toolchain/check/context.cpp b/toolchain/check/context.cpp
index 784184bbbd45..7eca3f2e05e8 100644
--- a/toolchain/check/context.cpp
+++ b/toolchain/check/context.cpp
@@ -821,7 +821,7 @@ class TypeCompleter {
     CARBON_CHECK(value_rep.kind != SemIR::ValueRepr::Unknown)
         << "Complete type should have a value representation";
     return value_rep;
-  };
+  }
 
   auto BuildBuiltinValueRepr(SemIR::TypeId type_id,
                              SemIR::Builtin builtin) const -> SemIR::ValueRepr {
diff --git a/toolchain/install/install_paths.h b/toolchain/install/install_paths.h
index 3816f65a7806..9e3ade36e21f 100644
--- a/toolchain/install/install_paths.h
+++ b/toolchain/install/install_paths.h
@@ -91,7 +91,7 @@ class InstallPaths {
   // in the `StringRef` for inclusion in any user report.
   [[nodiscard]] auto error() const -> std::optional<llvm::StringRef> {
     return error_;
-  };
+  }
 
   // The computed installation prefix. This should correspond to the
   // `prefix_root` directory in Bazel's output, or to some prefix the toolchain
diff --git a/toolchain/lex/lex.cpp b/toolchain/lex/lex.cpp
index 231bc32d43c6..ef7722a8877b 100644
--- a/toolchain/lex/lex.cpp
+++ b/toolchain/lex/lex.cpp
@@ -600,7 +600,7 @@ static constexpr auto MakeDispatchTable() -> DispatchTableT {
   table['\n'] = &DispatchLexVerticalWhitespace;
 
   return table;
-};
+}
 
 static constexpr DispatchTableT DispatchTable = MakeDispatchTable();
 
diff --git a/toolchain/lex/numeric_literal.cpp b/toolchain/lex/numeric_literal.cpp
index 1be9ab820a6f..fd5777a4053d 100644
--- a/toolchain/lex/numeric_literal.cpp
+++ b/toolchain/lex/numeric_literal.cpp
@@ -379,7 +379,7 @@ auto NumericLiteral::Parser::CheckDigitSeparatorPlacement(
   if (remaining_digit_separators) {
     diagnose_irregular_digit_separators();
   }
-};
+}
 
 // Check that we don't have a '0' prefix on a non-zero decimal integer.
 auto NumericLiteral::Parser::CheckLeadingZero() -> bool {
diff --git a/toolchain/lex/token_kind.h b/toolchain/lex/token_kind.h
index 6db40b0a34a8..3b41fc2a408a 100644
--- a/toolchain/lex/token_kind.h
+++ b/toolchain/lex/token_kind.h
@@ -71,23 +71,23 @@ class TokenKind : public CARBON_ENUM_BASE(TokenKind) {
 
   // Test whether this kind of token is a one-character symbol whose character
   // is not part of any other symbol.
-  auto is_one_char_symbol() const -> bool { return IsOneCharSymbol[AsInt()]; };
+  auto is_one_char_symbol() const -> bool { return IsOneCharSymbol[AsInt()]; }
 
   // Test whether this kind of token is a keyword.
-  auto is_keyword() const -> bool { return IsKeyword[AsInt()]; };
+  auto is_keyword() const -> bool { return IsKeyword[AsInt()]; }
 
   // Test whether this kind of token is a sized type literal.
   auto is_sized_type_literal() const -> bool {
     return *this == TokenKind::IntTypeLiteral ||
            *this == TokenKind::UnsignedIntTypeLiteral ||
            *this == TokenKind::FloatTypeLiteral;
-  };
+  }
 
   // If this token kind has a fixed spelling when in source code, returns it.
   // Otherwise returns an empty string.
   auto fixed_spelling() const -> llvm::StringLiteral {
     return FixedSpelling[AsInt()];
-  };
+  }
 
   // Get the expected number of parse tree nodes that will be created for this
   // token.
diff --git a/toolchain/parse/context.h b/toolchain/parse/context.h
index fa666ba1bcc7..09a147b0ff38 100644
--- a/toolchain/parse/context.h
+++ b/toolchain/parse/context.h
@@ -56,7 +56,7 @@ class Context {
     auto Print(llvm::raw_ostream& output) const -> void {
       output << state << " @" << token << " subtree_start=" << subtree_start
              << " has_error=" << has_error;
-    };
+    }
 
     // The state.
     State state;
diff --git a/toolchain/testing/file_test.cpp b/toolchain/testing/file_test.cpp
index 0b5daa53a6d6..fc2f119a01d9 100644
--- a/toolchain/testing/file_test.cpp
+++ b/toolchain/testing/file_test.cpp
@@ -161,7 +161,7 @@ class ToolchainFileTest : public FileTestBase {
 
 }  // namespace
 
-CARBON_FILE_TEST_FACTORY(ToolchainFileTest);
+CARBON_FILE_TEST_FACTORY(ToolchainFileTest)
 
 }  // namespace Carbon::Testing