diff --git a/src/main/java/net/kemitix/text/fit/NotEnoughSpace.java b/src/main/java/net/kemitix/text/fit/NotEnoughSpace.java
new file mode 100644
index 0000000..f3defe5
--- /dev/null
+++ b/src/main/java/net/kemitix/text/fit/NotEnoughSpace.java
@@ -0,0 +1,10 @@
+package net.kemitix.text.fit;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@Getter
+@RequiredArgsConstructor
+public class NotEnoughSpace extends RuntimeException {
+    private final int excessWordCount;
+}
diff --git a/src/main/java/net/kemitix/text/fit/TextLineWrapImpl.java b/src/main/java/net/kemitix/text/fit/TextLineWrapImpl.java
index 2357acb..001b5f3 100644
--- a/src/main/java/net/kemitix/text/fit/TextLineWrapImpl.java
+++ b/src/main/java/net/kemitix/text/fit/TextLineWrapImpl.java
@@ -41,7 +41,7 @@ class TextLineWrapImpl implements WordWrapper {
             List<Rectangle2D> boxes
     ) {
         Deque<Word> wordQ = new ArrayDeque<>(words);
-        return boxes.stream()
+        List<List<String>> wrappings = boxes.stream()
                 .map(rectangle2D -> {
                     double width = rectangle2D.getWidth();
                     double height = rectangle2D.getHeight();
@@ -68,6 +68,10 @@ class TextLineWrapImpl implements WordWrapper {
                     lines.add(wordsAsString(lineQ));
                     return removeBlankLines(lines);
                 }).collect(Collectors.toList());
+        if (wordQ.isEmpty()) {
+            return wrappings;
+        }
+        throw new NotEnoughSpace(wordQ.size());
     }
 
     private List<String> removeBlankLines(List<String> lines) {
diff --git a/src/main/java/net/kemitix/text/fit/WordWrapper.java b/src/main/java/net/kemitix/text/fit/WordWrapper.java
index b17ffa1..cd41e7f 100644
--- a/src/main/java/net/kemitix/text/fit/WordWrapper.java
+++ b/src/main/java/net/kemitix/text/fit/WordWrapper.java
@@ -5,12 +5,37 @@ import java.awt.geom.Rectangle2D;
 import java.util.List;
 
 public interface WordWrapper {
+    /**
+     * Wraps the text using the font in the graphics context to fit within the
+     * width.
+     *
+     * @param text the text to be line wrapped
+     * @param font the font to calculate character widths from
+     * @param graphics2D the context into which the font would be rendered
+     * @param width the maximum width of each line in pixels
+     * @return a list of the each line of text
+     * @throws NotEnoughSpace if there are more than {@link Integer#MAX_VALUE}
+     * lines - so not likely.
+     */
     List<String> wrap(
             String text,
             Font font,
             Graphics2D graphics2D,
             int width
     );
+
+    /**
+     * Wraps the text using the font in the graphics context to fit within the
+     * boxes, filling them in order.
+     *
+     * @param text the text to be line wrapped
+     * @param font the font to calculate character widths from
+     * @param graphics2D the context into which the font would be rendered
+     * @param boxes the list of rectangles to fit each line within.
+     * @return a list of the each line of text
+     * @throws NotEnoughSpace if there are more lines than can be fitted in the
+     * boxes provided.
+     */
     List<List<String>> wrap(
             String text,
             Font font,
diff --git a/src/test/java/net/kemitix/text/fit/TextLineWrapTest.java b/src/test/java/net/kemitix/text/fit/TextLineWrapTest.java
index 8314a2c..30ac6b8 100644
--- a/src/test/java/net/kemitix/text/fit/TextLineWrapTest.java
+++ b/src/test/java/net/kemitix/text/fit/TextLineWrapTest.java
@@ -199,9 +199,12 @@ public class TextLineWrapTest
             @DisplayName("Text overflows the box")
             public void tooManyLinesForBox() {
                 String lineOfWords = words(wordsPerLine, WORD);
-                assertThatExceptionOfType(IllegalArgumentException.class)
-                        .isThrownBy(() ->
-                                words(linesPerBox + 1, lineOfWords));
+                String input = words(linesPerBox + 1, lineOfWords);
+                assertThatExceptionOfType(NotEnoughSpace.class)
+                        .isThrownBy(() -> wrap(input))
+                        .satisfies(error ->
+                                assertThat(error.getExcessWordCount())
+                                        .isEqualTo(wordsPerLine));
             }
         }