diff --git a/lib/Epub/Epub/Section.cpp b/lib/Epub/Epub/Section.cpp
index 9365df20..7c0b3c12 100644
--- a/lib/Epub/Epub/Section.cpp
+++ b/lib/Epub/Epub/Section.cpp
@@ -10,7 +10,7 @@
 #include "parsers/ChapterHtmlSlimParser.h"
 
 namespace {
-constexpr uint8_t SECTION_FILE_VERSION = 18;
+constexpr uint8_t SECTION_FILE_VERSION = 19;
 constexpr uint32_t HEADER_SIZE = sizeof(uint8_t) + sizeof(int) + sizeof(float) + sizeof(bool) + sizeof(uint8_t) +
                                  sizeof(uint16_t) + sizeof(uint16_t) + sizeof(uint16_t) + sizeof(bool) + sizeof(bool) +
                                  sizeof(uint8_t) + sizeof(uint32_t) + sizeof(uint32_t);
diff --git a/lib/Epub/Epub/hyphenation/Hyphenator.cpp b/lib/Epub/Epub/hyphenation/Hyphenator.cpp
index 4ae5307e..ad5de454 100644
--- a/lib/Epub/Epub/hyphenation/Hyphenator.cpp
+++ b/lib/Epub/Epub/hyphenation/Hyphenator.cpp
@@ -12,11 +12,24 @@ const LanguageHyphenator* Hyphenator::cachedHyphenator_ = nullptr;
 
 namespace {
 
-// Maps a BCP-47 language tag to a language-specific hyphenator.
+// Normalize ISO 639-2 (three-letter) codes to ISO 639-1 (two-letter) codes used by the
+// hyphenation registry.  EPUBs may use either form in their dc:language metadata (e.g.
+// "eng" instead of "en").  Both the bibliographic ("fre"/"ger") and terminological
+// ("fra"/"deu") ISO 639-2 variants are mapped.
+struct Iso639Mapping {
+  const char* iso639_2;
+  const char* iso639_1;
+};
+static constexpr Iso639Mapping kIso639Mappings[] = {
+    {"eng", "en"}, {"fra", "fr"}, {"fre", "fr"}, {"deu", "de"}, {"ger", "de"},
+    {"rus", "ru"}, {"spa", "es"}, {"ita", "it"}, {"ukr", "uk"},
+};
+
+// Maps a BCP-47 or ISO 639-2 language tag to a language-specific hyphenator.
 const LanguageHyphenator* hyphenatorForLanguage(const std::string& langTag) {
   if (langTag.empty()) return nullptr;
 
-  // Extract primary subtag and normalize to lowercase (e.g., "en-US" -> "en").
+  // Extract primary subtag and normalize to lowercase (e.g., "en-US" -> "en", "ENG" -> "en").
   std::string primary;
   primary.reserve(langTag.size());
   for (char c : langTag) {
@@ -26,6 +39,14 @@ const LanguageHyphenator* hyphenatorForLanguage(const std::string& langTag) {
   }
   if (primary.empty()) return nullptr;
 
+  // Normalize ISO 639-2 three-letter codes to two-letter equivalents.
+  for (const auto& mapping : kIso639Mappings) {
+    if (primary == mapping.iso639_2) {
+      primary = mapping.iso639_1;
+      break;
+    }
+  }
+
   return getLanguageHyphenatorForPrimaryTag(primary);
 }