2 files changed, 9 insertions, 7 deletions
diff --git a/src/main/java/org/zwobble/mammoth/internal/docx/EmbeddedStyleMap.java b/src/main/java/org/zwobble/mammoth/internal/docx/EmbeddedStyleMap.java
index 4acce3f..fc8bfb1 100644
--- a/src/main/java/org/zwobble/mammoth/internal/docx/EmbeddedStyleMap.java
+++ b/src/main/java/org/zwobble/mammoth/internal/docx/EmbeddedStyleMap.java
@@ -11,6 +11,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
+import java.util.OptionalInt;
 
 import static org.zwobble.mammoth.internal.util.Casts.tryCast;
 import static org.zwobble.mammoth.internal.util.Iterables.findIndex;
@@ -64,7 +65,7 @@ public class EmbeddedStyleMap {
     }
 
     private static XmlElement updateOrAddElement(XmlElement parent, XmlElement element, String identifyingAttribute) {
-        int index = findIndex(parent.getChildren(), child ->
+        OptionalInt index = findIndex(parent.getChildren(), child ->
             tryCast(XmlElement.class, child)
                 .map(childElement ->
                     childElement.getName().equals(element.getName()) &&
@@ -74,10 +75,10 @@ public class EmbeddedStyleMap {
         );
         List<XmlNode> children = new ArrayList<>(parent.getChildren());
 
-        if (index == -1) {
-            children.add(element);
+        if (index.isPresent()) {
+            children.set(index.getAsInt(), element);
         } else {
-            children.set(index, element);
+            children.add(element);
         }
         return new XmlElement(parent.getName(), parent.getAttributes(), children);
     }
diff --git a/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
index 85fdaee..205f6a2 100644
--- a/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
+++ b/src/main/java/org/zwobble/mammoth/internal/util/Iterables.java
@@ -2,6 +2,7 @@ package org.zwobble.mammoth.internal.util;
 
 import java.util.Iterator;
 import java.util.Optional;
+import java.util.OptionalInt;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -153,14 +154,14 @@ public class Iterables {
         return StreamSupport.stream(iterable.spliterator(), false);
     }
 
-    public static <T> int findIndex(Iterable<T> iterable, Predicate<T> predicate) {
+    public static <T> OptionalInt findIndex(Iterable<T> iterable, Predicate<T> predicate) {
         int index = 0;
         for (T element : iterable) {
             if (predicate.test(element)) {
-                return index;
+                return OptionalInt.of(index);
             }
             index++;
         }
-        return -1;
+        return OptionalInt.empty();
     }
 }