diff --git a/src/generator/com/elovirta/pdf/merge.xsl b/src/generator/com/elovirta/pdf/merge.xsl
index 348e77e..3e6d33e 100644
--- a/src/generator/com/elovirta/pdf/merge.xsl
+++ b/src/generator/com/elovirta/pdf/merge.xsl
@@ -22,7 +22,10 @@
     <xsl:variable name="current" select="x:normalize(x:flatten($base), (), $url)"/>
     <xsl:choose>
       <xsl:when test="map:contains($base, 'extends') and $base ?extends eq 'default'">
-        <xsl:sequence select="json-doc(xs:anyURI('classpath:/com/elovirta/pdf/default.json'))"/>
+        <xsl:variable name="extends-url" select="xs:anyURI('classpath:/com/elovirta/pdf/default.json')"/>
+        <xsl:variable name="extends" select="x:normalize(x:flatten(json-doc($extends-url)), (), $url)"/>
+        <xsl:sequence select="map:merge(($current, $extends),
+                                        map{ 'duplicates': 'use-first' })"/>
       </xsl:when>
       <xsl:when test="map:contains($base, 'extends')">
         <xsl:variable name="extends-url" select="resolve-uri($base ?extends, $url)"/>
diff --git a/src/main/java/com/elovirta/pdf/ant/StylesheetGeneratorTask.java b/src/main/java/com/elovirta/pdf/ant/StylesheetGeneratorTask.java
index abd4c5d..79ce4ef 100644
--- a/src/main/java/com/elovirta/pdf/ant/StylesheetGeneratorTask.java
+++ b/src/main/java/com/elovirta/pdf/ant/StylesheetGeneratorTask.java
@@ -12,11 +12,13 @@
 
 import javax.xml.transform.TransformerException;
 import javax.xml.transform.URIResolver;
-import java.io.*;
+import java.io.File;
+import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Files;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonMap;
@@ -28,7 +30,9 @@ public class StylesheetGeneratorTask extends Task {
     private static final QName ATTR = QName.fromClarkName("{}attr");
     private static final QName VERSION = QName.fromClarkName("{}version");
     private static final QName FORMATTER = QName.fromClarkName("{}formatter");
-    /** Magic extends for build-in theme. */
+    /**
+     * Magic extends for build-in theme.
+     */
     private static final String DEFAULT_EXTENDS = "default";
     private static final URI DEFAULT_EXTENDS_URI = URI.create("classpath:/com/elovirta/pdf/default.json");
 
@@ -38,6 +42,7 @@ public class StylesheetGeneratorTask extends Task {
     private URIResolver resolver;
     private Processor processor;
     private XsltCompiler compiler;
+    private Xslt30Transformer transformer;
     private XPathCompiler xpathCompiler;
     private ObjectMapper yamlReader;
     private ObjectMapper jsonWriter;
@@ -53,6 +58,12 @@ public void init() {
         processor = xmlUtils.getProcessor();
         compiler = processor.newXsltCompiler();
         compiler.setURIResolver(resolver);
+        try {
+            final XsltExecutable executable = compiler.compile(resolver.resolve("classpath:/com/elovirta/pdf/merge.xsl", null));
+            transformer = executable.load30();
+        } catch (SaxonApiException | TransformerException e) {
+            throw new BuildException(String.format("Failed to parse template %s", template), e);
+        }
         xpathCompiler = processor.newXPathCompiler();
         yamlReader = new ObjectMapper(new YAMLFactory());
         jsonWriter = new ObjectMapper();
@@ -69,6 +80,7 @@ public void execute() throws BuildException {
         }
 
         final XdmItem xdmItem = parseTemplate();
+        getProject().log("Template:" + xdmItem, Project.MSG_INFO);
         generate(xdmItem, "front-matter.xsl", "xsl/fo/front-matter.xsl", null);
         generate(xdmItem, "commons.xsl", "xsl/fo/commons.xsl", null);
         generate(xdmItem, "tables.xsl", "xsl/fo/tables.xsl", null);
@@ -150,24 +162,18 @@ File generate(final XdmItem xdmItem,
     XdmItem parseTemplate() {
         getProject().log(this, String.format("Reading %s", template.toURI()), Project.MSG_INFO);
         final String name = template.getName().toLowerCase();
-        try {
-            final XsltExecutable executable = compiler.compile(resolver.resolve("classpath:/com/elovirta/pdf/merge.xsl", null));
-            final XdmItem merged;
-            // XXX: Saxon's JSON functions don't use URIResolver, so have to parse manually
-            if (name.endsWith(".yml") || name.endsWith(".yaml")) {
-                merged = parseYamlTemplate(executable, parseYaml(template.toURI()), template.toURI());
-            } else {
-                merged = parseJsonTemplate();
-            }
-            return resolveVariables(executable, merged);
-        } catch (SaxonApiException | TransformerException e) {
-            throw new BuildException(String.format("Failed to parse template %s", template), e);
+        final XdmItem merged;
+        // XXX: Saxon's JSON functions don't use URIResolver, so have to parse manually
+        if (name.endsWith(".yml") || name.endsWith(".yaml")) {
+            merged = parseYamlTemplate(parseYaml(template.toURI()), template.toURI());
+        } else {
+            merged = parseJsonTemplate();
         }
+        return resolveVariables(merged);
     }
 
-    private XdmItem resolveVariables(final XsltExecutable executable, final XdmItem base) {
+    private XdmItem resolveVariables(final XdmItem base) {
         try {
-            final Xslt30Transformer transformer = executable.load30();
             final XdmValue resolved = transformer.callFunction(QName.fromClarkName("{x}resolve"), new XdmValue[]{
                     base
             });
@@ -182,6 +188,7 @@ private XdmItem resolveVariables(final XsltExecutable executable, final XdmItem
 
     private XdmItem parseJsonTemplate() {
         try {
+            new JsonBuilder(xmlUtils.getProcessor().getUnderlyingConfiguration());
             final XdmItem theme = xpathCompiler.evaluateSingle("json-doc(.)", new XdmAtomicValue(template.toURI()));
             final XsltExecutable executable = compiler.compile(resolver.resolve("classpath:/com/elovirta/pdf/merge.xsl", null));
             final Xslt30Transformer transformer = executable.load30();
@@ -196,54 +203,53 @@ private XdmItem parseJsonTemplate() {
         }
     }
 
-    private XdmItem parseYamlTemplate(final XsltExecutable executable, final XdmItem base, final URI url) {
+    private XdmItem parseYamlTemplate(final XdmItem base, final URI url) {
         try {
-            final Xslt30Transformer transformer = executable.load30();
             final XdmItem extendsValue = xpathCompiler.evaluateSingle(". ?extends", base);
             if (extendsValue != null && extendsValue.getStringValue().equals(DEFAULT_EXTENDS)) {
-                final XdmItem extendsRes = xpathCompiler.evaluateSingle("json-doc(.)", new XdmAtomicValue(DEFAULT_EXTENDS_URI));
+                final XPathSelector selector = xpathCompiler.compile("json-doc(.)").load();
+                selector.setURIResolver(resolver);
+                selector.setContextItem(new XdmAtomicValue(DEFAULT_EXTENDS_URI));
+                final XdmItem extendsRes = selector.evaluateSingle();
+//                final XdmItem extendsRes = xpathCompiler.evaluateSingle("json-doc(.)", new XdmAtomicValue(DEFAULT_EXTENDS_URI));
 
-                final XdmValue flattened = transformer.callFunction(QName.fromClarkName("{x}flatten"), new XdmValue[]{
-                        base
-                });
-                final XdmValue normalized = transformer.callFunction(QName.fromClarkName("{x}normalize"), new XdmValue[]{
-                        flattened, XdmEmptySequence.getInstance(), new XdmAtomicValue(DEFAULT_EXTENDS_URI)
-                });
-                return normalized.itemAt(0);
+                return transformer.callFunction(QName.fromClarkName("{x}merge"), new XdmValue[]{
+                        normalize(extendsRes),
+                        normalize(base)
+                }).itemAt(0);
             } else if (extendsValue != null) {
                 final URI extendsUri = url.resolve(extendsValue.getStringValue());
-                final XdmItem extendsRes = parseYamlTemplate(executable, parseYaml(extendsUri), url);
+                final XdmItem extendsRes = parseYamlTemplate(parseYaml(extendsUri), url);
 
-                final XdmValue flattened = transformer.callFunction(QName.fromClarkName("{x}flatten"), new XdmValue[]{
-                        base
-                });
-                final XdmValue normalized = transformer.callFunction(QName.fromClarkName("{x}normalize"), new XdmValue[]{
-                        flattened, XdmEmptySequence.getInstance(), new XdmAtomicValue(extendsUri)
-                });
                 return transformer.callFunction(QName.fromClarkName("{x}merge"), new XdmValue[]{
-                        extendsRes.stream().asXdmValue(), normalized
+                        extendsRes, normalize(base)
                 }).itemAt(0);
             } else {
-                final XdmValue flattened = transformer.callFunction(QName.fromClarkName("{x}flatten"), new XdmValue[]{
-                        base
-                });
-                final XdmValue normalized = transformer.callFunction(QName.fromClarkName("{x}normalize"), new XdmValue[]{
-                        flattened, XdmEmptySequence.getInstance(), new XdmAtomicValue(url)
-                });
-                return normalized.itemAt(0);
+                return normalize(base).itemAt(0);
             }
         } catch (SaxonApiException e) {
             throw new BuildException(String.format("Failed to parse template %s", template), e);
         }
     }
 
+    private XdmItem normalize(XdmItem in) {
+        try {
+            return transformer.callFunction(QName.fromClarkName("{x}normalize"), new XdmValue[]{
+                    transformer.callFunction(QName.fromClarkName("{x}flatten"), new XdmValue[]{
+                            in
+                    }), XdmEmptySequence.getInstance(), new XdmAtomicValue(DEFAULT_EXTENDS_URI)
+            }).itemAt(0);
+        } catch (SaxonApiException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     private XdmItem parseYaml(final URI abs) {
         try {
             final Object yaml = yamlReader.readValue(abs.toURL(), Object.class);
             final String json = jsonWriter.writeValueAsString(yaml);
             return xpathCompiler.evaluateSingle("parse-json(.)", new XdmAtomicValue(json));
         } catch (SaxonApiException | IOException e) {
-            e.printStackTrace();
             throw new BuildException("Failed to convert YAML to JSON: " + e.getMessage(), e);
         }
     }
diff --git a/src/main/resources/com/elovirta/pdf/default.json b/src/main/resources/com/elovirta/pdf/default.json
index 9d3b971..3456a45 100644
--- a/src/main/resources/com/elovirta/pdf/default.json
+++ b/src/main/resources/com/elovirta/pdf/default.json
@@ -1,7 +1,7 @@
 {
   "style": {
-    "toc-1": {
-      "color": "pink"
+    "h1": {
+      "font-weight": "bold"
     }
   }
 }
diff --git a/src/test/java/com/elovirta/pdf/ant/StylesheetGeneratorTaskTest.java b/src/test/java/com/elovirta/pdf/ant/StylesheetGeneratorTaskTest.java
index 811ab34..53550e3 100644
--- a/src/test/java/com/elovirta/pdf/ant/StylesheetGeneratorTaskTest.java
+++ b/src/test/java/com/elovirta/pdf/ant/StylesheetGeneratorTaskTest.java
@@ -5,7 +5,6 @@
 import org.dita.dost.log.DITAOTAntLogger;
 import org.dita.dost.util.XMLUtils;
 import org.json.JSONException;
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.io.TempDir;
 import org.junit.jupiter.params.ParameterizedTest;
@@ -13,7 +12,6 @@
 import org.skyscreamer.jsonassert.JSONCompareMode;
 
 import java.io.*;
-import java.net.URI;
 import java.net.URISyntaxException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
@@ -34,6 +32,7 @@ public class StylesheetGeneratorTaskTest {
     @BeforeEach
     public void setUp() {
         xmlUtils = new XMLUtils();
+        xmlUtils.getProcessor().getUnderlyingConfiguration().setURIResolver(resolver);
         xpathCompiler = xmlUtils.getProcessor().newXPathCompiler();
         final Project project = new Project();
         xmlUtils.setLogger(new DITAOTAntLogger(project));
@@ -174,6 +173,20 @@ public void getTemplate_normalize_single(final String template) throws URISyntax
                 JSONCompareMode.STRICT);
     }
 
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "default.json",
+            "default.yaml"
+    })
+    public void getTemplate_default(final String template) throws URISyntaxException, SaxonApiException, JSONException {
+        task.setTemplate(new File(getClass().getClassLoader().getResource("src/" + template).toURI()).getAbsolutePath());
+
+        final XdmValue act = task.parseTemplate();
+
+        assertEquals(readToString("exp/" + template.substring(0, template.indexOf(".")) + ".json"), toString(act),
+                JSONCompareMode.STRICT);
+    }
+
     private String readToString(final String name) {
         final InputStream baseInput = getClass().getClassLoader().getResourceAsStream(name);
         return new BufferedReader(new InputStreamReader(baseInput, StandardCharsets.UTF_8))
diff --git a/src/test/resources/com/elovirta/pdf/default.json b/src/test/resources/com/elovirta/pdf/default.json
new file mode 100644
index 0000000..ce30cb3
--- /dev/null
+++ b/src/test/resources/com/elovirta/pdf/default.json
@@ -0,0 +1,7 @@
+{
+  "style": {
+    "h1": {
+      "font-weight": "bold",
+    }
+  }
+}
diff --git a/src/test/resources/exp/default.json b/src/test/resources/exp/default.json
new file mode 100644
index 0000000..e7bb2b7
--- /dev/null
+++ b/src/test/resources/exp/default.json
@@ -0,0 +1,10 @@
+{
+  "style": {
+    "toc-1": {
+      "color": "blue"
+    },
+    "toc-2": {
+      "color": "green"
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/test/resources/src/default.json b/src/test/resources/src/default.json
new file mode 100644
index 0000000..791dd7a
--- /dev/null
+++ b/src/test/resources/src/default.json
@@ -0,0 +1,8 @@
+{
+  "extends": "default",
+  "style": {
+    "h1": {
+      "background-color": "pink"
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/test/resources/src/default.yaml b/src/test/resources/src/default.yaml
new file mode 100644
index 0000000..b083efd
--- /dev/null
+++ b/src/test/resources/src/default.yaml
@@ -0,0 +1,4 @@
+extends: default
+style:
+  h1:
+    background-color: pink