diff --git a/src/odr/internal/common/element_registry.hpp b/src/odr/internal/common/element_registry.hpp
index 4436c1367..11f8b8c36 100644
--- a/src/odr/internal/common/element_registry.hpp
+++ b/src/odr/internal/common/element_registry.hpp
@@ -58,6 +58,9 @@ template <typename T, typename Id = ElementIdentifier>
 class SortedSideTable final {
 public:
   T &emplace(const ElementIdentifier id, T value) {
+    if (id > std::numeric_limits<Id>::max()) {
+      throw std::out_of_range("SortedSideTable::emplace: identifier too wide");
+    }
     if (!m_entries.empty() && m_entries.back().first >= id) {
       throw std::invalid_argument(
           "SortedSideTable::emplace: identifier out of order");
diff --git a/src/odr/internal/common/text_cursor.hpp b/src/odr/internal/common/text_cursor.hpp
index a1e13422e..3fd0a863e 100644
--- a/src/odr/internal/common/text_cursor.hpp
+++ b/src/odr/internal/common/text_cursor.hpp
@@ -3,6 +3,7 @@
 #include <odr/internal/util/string_util.hpp>
 
 #include <cstddef>
+#include <stdexcept>
 #include <string_view>
 
 namespace odr::internal {
@@ -32,7 +33,12 @@ class TextCursor {
     return c;
   }
 
-  void advance(const std::size_t count) { m_rest.remove_prefix(count); }
+  void advance(const std::size_t count) {
+    if (count > m_rest.size()) {
+      throw std::out_of_range("TextCursor::advance: past end of input");
+    }
+    m_rest.remove_prefix(count);
+  }
 
   /// Back to a view @ref rest answered earlier, undoing what was read since.
   void seek(const std::string_view at) { m_rest = at; }
@@ -46,7 +52,7 @@ class TextCursor {
   /// Whitespace ahead of it is filler; the text itself is the token.
   [[nodiscard]] bool consume(const char c) {
     skip_whitespace();
-    if (peek() != c) {
+    if (empty() || peek() != c) {
       return false;
     }
     advance(1);
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index e230dca1c..0f5566c00 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -54,12 +54,14 @@ add_executable(odr_test
 
         "src/internal/cfb/cfb_archive_test.cpp"
 
+        "src/internal/common/element_registry_test.cpp"
         "src/internal/common/filesystem_test.cpp"
         "src/internal/common/list_numbering_test.cpp"
         "src/internal/common/path_test.cpp"
         "src/internal/common/table_cursor_test.cpp"
         "src/internal/common/sheet_cell_source_test.cpp"
         "src/internal/common/table_range_test.cpp"
+        "src/internal/common/text_cursor_test.cpp"
 
         "src/internal/crypto/crypto_util_test.cpp"
 
diff --git a/test/src/internal/common/element_registry_test.cpp b/test/src/internal/common/element_registry_test.cpp
new file mode 100644
index 000000000..7785ebe4f
--- /dev/null
+++ b/test/src/internal/common/element_registry_test.cpp
@@ -0,0 +1,23 @@
+#include <odr/internal/common/element_registry.hpp>
+
+#include <gtest/gtest.h>
+
+#include <cstdint>
+#include <limits>
+#include <stdexcept>
+
+using namespace odr::internal;
+
+TEST(SortedSideTable, rejects_wide_ids_without_corrupting_order) {
+  SortedSideTable<std::uint32_t, std::uint8_t> table;
+  table.emplace(1, 10);
+  table.emplace(255, 20);
+  EXPECT_THROW(table.emplace(256, 30), std::out_of_range);
+  EXPECT_THROW(
+      table.emplace(std::numeric_limits<odr::ElementIdentifier>::max(), 40),
+      std::out_of_range);
+  EXPECT_EQ(table.at(1), 10);
+  EXPECT_EQ(table.at(255), 20);
+  EXPECT_EQ(table.find(256), nullptr);
+  EXPECT_EQ(table.find(0), nullptr);
+}
diff --git a/test/src/internal/common/text_cursor_test.cpp b/test/src/internal/common/text_cursor_test.cpp
new file mode 100644
index 000000000..dcd3b004f
--- /dev/null
+++ b/test/src/internal/common/text_cursor_test.cpp
@@ -0,0 +1,20 @@
+#include <odr/internal/common/text_cursor.hpp>
+
+#include <gtest/gtest.h>
+
+#include <stdexcept>
+#include <string_view>
+
+using namespace odr::internal;
+
+TEST(TextCursor, rejects_overread_and_distinguishes_nul_from_end) {
+  TextCursor cursor(std::string_view("\0x", 2));
+  EXPECT_THROW(cursor.advance(3), std::out_of_range);
+  EXPECT_EQ(cursor.rest().size(), 2);
+  EXPECT_TRUE(cursor.consume('\0'));
+  EXPECT_EQ(cursor.take(), 'x');
+  EXPECT_FALSE(cursor.consume('\0'));
+  EXPECT_TRUE(cursor.empty());
+  EXPECT_NO_THROW(cursor.advance(0));
+  EXPECT_THROW(cursor.advance(1), std::out_of_range);
+}