diff --git a/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileSystemWatcher.java b/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileSystemWatcher.java
index 7531e4ee04..0f46a0c0e9 100644
--- a/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileSystemWatcher.java
+++ b/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/filewatch/FileSystemWatcher.java
@@ -114,7 +114,8 @@ public class FileSystemWatcher {
 	 */
 	public synchronized void addSourceFolder(File folder) {
 		Assert.notNull(folder, "Folder must not be null");
-		Assert.isTrue(folder.isDirectory(), "Folder must not be a file");
+		Assert.isTrue(folder.isDirectory(), "Folder '" + folder + "' must exist and must"
+				+ " be a directory");
 		checkNotStarted();
 		this.folders.put(folder, null);
 	}
diff --git a/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/filewatch/FileSystemWatcherTests.java b/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/filewatch/FileSystemWatcherTests.java
index 1af417ffad..37e799e59f 100644
--- a/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/filewatch/FileSystemWatcherTests.java
+++ b/spring-boot-devtools/src/test/java/org/springframework/boot/devtools/filewatch/FileSystemWatcherTests.java
@@ -38,6 +38,7 @@ import org.springframework.util.FileCopyUtils;
 
 import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 import static org.mockito.Mockito.mock;
@@ -107,6 +108,25 @@ public class FileSystemWatcherTests {
 		this.watcher.addSourceFolder(null);
 	}
 
+	@Test
+	public void sourceFolderMustExist() throws Exception {
+		File folder = new File("does/not/exist");
+		assertThat(folder.exists(), is(false));
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown
+				.expectMessage("Folder 'does/not/exist' must exist and must be a directory");
+		this.watcher.addSourceFolder(folder);
+	}
+
+	@Test
+	public void sourceFolderMustBeADirectory() throws Exception {
+		File folder = new File("pom.xml");
+		assertThat(folder.isFile(), is(true));
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Folder 'pom.xml' must exist and must be a directory");
+		this.watcher.addSourceFolder(new File("pom.xml"));
+	}
+
 	@Test
 	public void cannotAddSourceFolderToStartedListener() throws Exception {
 		this.thrown.expect(IllegalStateException.class);