diff --git a/lib/Epub/Epub/css/CssParser.cpp b/lib/Epub/Epub/css/CssParser.cpp
index 77ee8e77..64939fc8 100644
--- a/lib/Epub/Epub/css/CssParser.cpp
+++ b/lib/Epub/Epub/css/CssParser.cpp
@@ -431,6 +431,11 @@ CssStyle CssParser::parseDeclarations(std::string_view declBlock) {
 // Rule processing
 
 void CssParser::processRuleBlockWithStyle(std::string_view selectorGroup, const CssStyle& style) {
+  // Skip rules that don't define any supported properties to save RAM.
+  if (!style.defined.anySet()) {
+    return;
+  }
+
   // Check if we've reached the rule limit before processing
   if (rulesBySelector_.size() >= MAX_RULES) {
     LOG_DBG("CSS", "Reached max rules limit (%zu), stopping CSS parsing", MAX_RULES);
diff --git a/lib/Epub/Epub/css/CssParser.h b/lib/Epub/Epub/css/CssParser.h
index 41797fd3..892216b3 100644
--- a/lib/Epub/Epub/css/CssParser.h
+++ b/lib/Epub/Epub/css/CssParser.h
@@ -33,7 +33,7 @@
 class CssParser {
  public:
   // Bump when CSS cache format or rules change; section caches are invalidated when this changes
-  static constexpr uint8_t CSS_CACHE_VERSION = 7;
+  static constexpr uint8_t CSS_CACHE_VERSION = 8;
 
   explicit CssParser(std::string cachePath) : cachePath(std::move(cachePath)) {}
   ~CssParser() = default;