diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b08b72..a4ca7f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 * Removed OffsetAwareRuleSet, it's a RuleSet with optional attributes filename and offset
 * Improved performance of block parsing by using StringScanner
 * Improve `RuleSet#parse_declarations!` performance by using substring search istead of regexps
+* Fix error when parsing values consisting of `!important` only
 
 ### Version v1.18.0
 
diff --git a/lib/css_parser/rule_set.rb b/lib/css_parser/rule_set.rb
index 82c7a99..8f3224f 100644
--- a/lib/css_parser/rule_set.rb
+++ b/lib/css_parser/rule_set.rb
@@ -667,7 +667,7 @@ def parse_declarations!(block) # :nodoc:
         value = decs[(colon + 1)..]
         property.strip!
         value.strip!
-        next if property.empty? || value.empty?
+        next if property.empty? || value.empty? || value.start_with?(CssParser::IMPORTANT_IN_PROPERTY_RX)
 
         add_declaration!(property, value)
         continuation = nil
diff --git a/test/test_css_parser_misc.rb b/test/test_css_parser_misc.rb
index 007a742..817c436 100644
--- a/test/test_css_parser_misc.rb
+++ b/test/test_css_parser_misc.rb
@@ -227,47 +227,58 @@ def test_enumerator_nonempty
     end
   end
 
+  def with_value_exception(&block)
+    # Raise synthetic exception to test error handling because there is no known way to cause it naturally
+    CssParser::RuleSet::Declarations::Value.stub :new, -> { raise ArgumentError.new, 'stub' }, &block
+  end
+
   def test_catching_argument_exceptions_for_add_rule
-    cp_with_exceptions = Parser.new(rule_set_exceptions: true)
-    assert_raises ArgumentError, 'background-color value is empty' do
-      cp_with_exceptions.add_rule!(selectors: 'body', block: 'background-color: !important')
-    end
+    with_value_exception do
+      cp_with_exceptions = Parser.new(rule_set_exceptions: true)
+      assert_raises ArgumentError, 'stub' do
+        cp_with_exceptions.add_rule!(selectors: 'body', block: 'background-color: blue')
+      end
 
-    cp_without_exceptions = Parser.new(rule_set_exceptions: false)
-    cp_without_exceptions.add_rule!(selectors: 'body', block: 'background-color: !important')
+      cp_without_exceptions = Parser.new(rule_set_exceptions: false)
+      cp_without_exceptions.add_rule!(selectors: 'body', block: 'background-color: blue')
+    end
   end
 
   def test_catching_argument_exceptions_for_add_rule_positional
-    cp_with_exceptions = Parser.new(rule_set_exceptions: true)
+    with_value_exception do
+      cp_with_exceptions = Parser.new(rule_set_exceptions: true)
+
+      assert_raises ArgumentError, 'stub' do
+        _, err = capture_io do
+          cp_with_exceptions.add_rule!('body', 'background-color: blue')
+        end
+        assert_includes err, "DEPRECATION"
+      end
 
-    assert_raises ArgumentError, 'background-color value is empty' do
+      cp_without_exceptions = Parser.new(rule_set_exceptions: false)
       _, err = capture_io do
-        cp_with_exceptions.add_rule!('body', 'background-color: !important')
+        cp_without_exceptions.add_rule!('body', 'background-color: blue')
       end
       assert_includes err, "DEPRECATION"
     end
-
-    cp_without_exceptions = Parser.new(rule_set_exceptions: false)
-    _, err = capture_io do
-      cp_without_exceptions.add_rule!('body', 'background-color: !important')
-    end
-    assert_includes err, "DEPRECATION"
   end
 
   def test_catching_argument_exceptions_for_add_rule_with_offsets
-    cp_with_exceptions = Parser.new(capture_offsets: true, rule_set_exceptions: true)
+    with_value_exception do
+      cp_with_exceptions = Parser.new(capture_offsets: true, rule_set_exceptions: true)
+
+      assert_raises ArgumentError, 'stub' do
+        _, err = capture_io do
+          cp_with_exceptions.add_rule_with_offsets!('body', 'background-color: blue', 'inline', 1)
+        end
+        assert_includes err, "DEPRECATION"
+      end
 
-    assert_raises ArgumentError, 'background-color value is empty' do
+      cp_without_exceptions = Parser.new(capture_offsets: true, rule_set_exceptions: false)
       _, err = capture_io do
-        cp_with_exceptions.add_rule_with_offsets!('body', 'background-color: !important', 'inline', 1)
+        cp_without_exceptions.add_rule_with_offsets!('body', 'background-color: blue', 'inline', 1)
       end
       assert_includes err, "DEPRECATION"
     end
-
-    cp_without_exceptions = Parser.new(capture_offsets: true, rule_set_exceptions: false)
-    _, err = capture_io do
-      cp_without_exceptions.add_rule_with_offsets!('body', 'background-color: !important', 'inline', 1)
-    end
-    assert_includes err, "DEPRECATION"
   end
 end
diff --git a/test/test_rule_set.rb b/test/test_rule_set.rb
index d1bf9aa..1a40c1f 100644
--- a/test/test_rule_set.rb
+++ b/test/test_rule_set.rb
@@ -122,6 +122,12 @@ def test_overriding_specificity
     end
   end
 
+  def test_important_without_value
+    declarations = 'color: !important; background-color: #fff'
+    rs = RuleSet.new(selectors: '#content p, a', block: declarations)
+    assert_equal('background-color: #fff;', rs.declarations_to_s)
+  end
+
   def test_not_raised_issue68
     ok = true
     begin