diff --git a/src/styleengine.cc b/src/styleengine.cc
index 7ccd4ed..5ae58d7 100644
--- a/src/styleengine.cc
+++ b/src/styleengine.cc
@@ -68,12 +68,12 @@ StyleEngine::StyleEngine (dw::core::Layout *layout,
    StyleAttrs style_attrs;
    FontAttrs font_attrs;
 
-   doctree = new Doctree ();
-   cssContext = new CssContext ();
+   doctree = std::make_unique< Doctree >();
+   cssContext = std::make_unique< CssContext >();
    buildUserStyle ();
    this->layout = layout;
-   this->pageUrl = pageUrl ? a_Url_dup(pageUrl).release() : nullptr;
-   this->baseUrl = baseUrl ? a_Url_dup(baseUrl).release() : nullptr;
+   this->pageUrl = pageUrl ? a_Url_dup(pageUrl) : nullptr;
+   this->baseUrl = baseUrl ? a_Url_dup(baseUrl) : nullptr;
    importDepth = 0;
    dpmm = layout->dpiX () / 25.4; /* assume dpiX == dpiY */
    this->zoom = zoom;
@@ -107,12 +107,6 @@ StyleEngine::~StyleEngine () {
 
    stackPop (); // dummy node on the bottom of the stack
    assert (stack.size () == 0);
-
-   delete pageUrl;
-   delete baseUrl;
-
-   delete doctree;
-   delete cssContext;
 }
 
 void StyleEngine::stackPush () {
@@ -199,7 +193,7 @@ void StyleEngine::setStyle (const char *styleAttr) {
       n->styleAttrProperties = std::make_unique< CssPropertyList >(true);
       n->styleAttrPropertiesImportant = new CssPropertyList (true);
 
-      CssParser::parseDeclarationBlock (baseUrl, styleAttr, strlen (styleAttr),
+      CssParser::parseDeclarationBlock (baseUrl.get(), styleAttr, strlen (styleAttr),
                                         n->styleAttrProperties.get(),
                                         n->styleAttrPropertiesImportant);
    }
@@ -766,7 +760,7 @@ void StyleEngine::apply (int i, StyleAttrs *attrs, CssPropertyList *props,
 
       // we use the pageUrl as requester to prevent cross
       // domain requests as specified in domainrc
-      DilloWeb *web = a_Web_new(bw, imgUrl.get(), pageUrl);
+      DilloWeb *web = a_Web_new(bw, imgUrl.get(), pageUrl.get());
       web->Image = std::move( image );
       web->flags |= WEB_Image;
 
@@ -934,7 +928,7 @@ Style * StyleEngine::style0 (int i, BrowserWindow *bw) {
    nonCssProperties = stack.at (i).nonCssProperties;
 
    // merge style information
-   cssContext->apply (&props, doctree, stack.at(i).doctreeNode,
+   cssContext->apply (&props, doctree.get(), stack.at(i).doctreeNode,
                       styleAttrProperties, styleAttrPropertiesImportant,
                       nonCssProperties);
 
@@ -1002,7 +996,7 @@ void StyleEngine::parse (DilloHtml *html, DilloUrl *url, const char *buf,
    }
 
    importDepth++;
-   CssParser::parse (html, url, cssContext, buf, buflen, origin);
+   CssParser::parse (html, url, cssContext.get(), buf, buflen, origin);
    importDepth--;
 }
 
@@ -1079,6 +1073,6 @@ void StyleEngine::buildUserStyle () {
 
    const std::string style= a_Misc_file2dstr(filename.c_str());
    if (not style.empty()) {
-      CssParser::parse (NULL,NULL,cssContext, style.c_str(), style.size(), CSS_ORIGIN_USER);
+      CssParser::parse( nullptr, nullptr, cssContext.get(), style.c_str(), style.size(), CSS_ORIGIN_USER );
    }
 }
diff --git a/src/styleengine.hh b/src/styleengine.hh
index ee45d75..388b90c 100644
--- a/src/styleengine.hh
+++ b/src/styleengine.hh
@@ -48,12 +48,13 @@ class StyleEngine {
 
       dw::core::Layout *layout;
       std::vector <Node> stack;
-      CssContext *cssContext;
-      Doctree *doctree;
+      std::unique_ptr< CssContext > cssContext;
+      std::unique_ptr< Doctree > doctree;
       int importDepth;
       float dpmm;
       float zoom;
-      DilloUrl *pageUrl, *baseUrl;
+      std::unique_ptr< DilloUrl > pageUrl;
+      std::unique_ptr< DilloUrl > baseUrl;
 
       void stackPush ();
       void stackPop ();