diff --git a/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java b/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
index 5ee5a31..4043008 100644
--- a/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/SitemapGenerator.java
@@ -260,8 +260,10 @@ abstract class SitemapGenerator<U extends ISitemapUrl, THIS extends SitemapGener
 			} else {
 				out = new OutputStreamWriter(new FileOutputStream(outFile), Charset.forName("UTF-8").newEncoder());
 			}
-			
+
 			writeSiteMap(out);
+			out.flush();
+
 			if (autoValidate) SitemapValidator.validateWebSitemap(outFile);
 		} catch (IOException e) {
 			throw new RuntimeException("Problem writing sitemap file " + outFile, e);
diff --git a/src/main/java/com/redfin/sitemapgenerator/SitemapIndexGenerator.java b/src/main/java/com/redfin/sitemapgenerator/SitemapIndexGenerator.java
index 0a44a6d..1d31f33 100644
--- a/src/main/java/com/redfin/sitemapgenerator/SitemapIndexGenerator.java
+++ b/src/main/java/com/redfin/sitemapgenerator/SitemapIndexGenerator.java
@@ -228,6 +228,8 @@ public class SitemapIndexGenerator {
                 // TODO gzip? is that legal for a sitemap index?
                 out = new FileWriter(outFile);
                 writeSiteMap(out);
+                out.flush();
+
                 if (autoValidate) SitemapValidator.validateSitemapIndex(outFile);
             } catch (IOException e) {
                 throw new RuntimeException("Problem writing sitemap index file " + outFile, e);