diff --git a/src/main/java/com/jthemedetecor/GnomeThemeDetector.java b/src/main/java/com/jthemedetecor/GnomeThemeDetector.java
index f8cbfde..4ee0abc 100644
--- a/src/main/java/com/jthemedetecor/GnomeThemeDetector.java
+++ b/src/main/java/com/jthemedetecor/GnomeThemeDetector.java
@@ -123,6 +123,12 @@ public void run() {
                     while (!this.isInterrupted()) {
                         //Expected input = gtk-theme: '$GtkThemeName'
                         String readLine = reader.readLine();
+                        
+                        // reader.readLine sometimes returns null on application shutdown.
+                        if (readLine == null) {
+                            continue;
+                        }
+                        
                         if (!outputPattern.matcher(readLine).matches()) {
                             continue;
                         }