diff --git a/language/assignments_spec.rb b/language/assignments_spec.rb
index 4ad9f4167..d469459c4 100644
--- a/language/assignments_spec.rb
+++ b/language/assignments_spec.rb
@@ -72,6 +72,34 @@ def []=(k, v, &block) @h[k] = v; end
         end
       end
     end
+
+    context "given keyword arguments" do
+      before do
+        @klass = Class.new do
+          attr_reader :x
+
+          def []=(*args, **kw)
+            @x = [args, kw]
+          end
+        end
+      end
+
+      ruby_version_is ""..."3.4" do
+        it "supports keyword arguments in index assignments" do
+          a = @klass.new
+          eval "a[1, 2, 3, b: 4] = 5"
+          a.x.should == [[1, 2, 3, {b: 4}, 5], {}]
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "raies SyntaxError when given keyword arguments in index assignments" do
+          a = @klass.new
+          -> { eval "a[1, 2, 3, b: 4] = 5" }.should raise_error(SyntaxError,
+            /keywords are not allowed in index assignment expressions|keyword arg given in index assignment/) # prism|parse.y
+        end
+      end
+    end
   end
 
   describe 'using +=' do
@@ -176,6 +204,46 @@ def []=(k, v, &block) @h[k] = v; end
         end
       end
 
+      context "given keyword arguments" do
+        before do
+          @klass = Class.new do
+            attr_reader :x
+
+            def [](*args)
+              100
+            end
+
+            def []=(*args, **kw)
+              @x = [args, kw]
+            end
+          end
+        end
+
+        ruby_version_is ""..."3.3" do
+          it "supports keyword arguments in index assignments" do
+            a = @klass.new
+            eval "a[1, 2, 3, b: 4] += 5"
+            a.x.should == [[1, 2, 3, {b: 4}, 105], {}]
+          end
+        end
+
+        ruby_version_is "3.3"..."3.4" do
+          it "supports keyword arguments in index assignments" do
+            a = @klass.new
+            eval "a[1, 2, 3, b: 4] += 5"
+            a.x.should == [[1, 2, 3, 105], {b: 4}]
+          end
+        end
+
+        ruby_version_is "3.4" do
+          it "raies SyntaxError when given keyword arguments in index assignments" do
+            a = @klass.new
+            -> { eval "a[1, 2, 3, b: 4] += 5" }.should raise_error(SyntaxError,
+              /keywords are not allowed in index assignment expressions|keyword arg given in index assignment/) # prism|parse.y
+          end
+        end
+      end
+
       context 'splatted argument' do
         it 'correctly handles it' do
           @b[:m] = 10