diff --git a/.circleci/config.yml b/.circleci/config.yml
index e9e4452ea17..f140a5511af 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -6,6 +6,8 @@ jobs:
       - image: circleci/openjdk:8-jdk
     steps:
       - checkout
+      - run: git submodule sync
+      - run: git submodule update --init
       - restore_cache:
           keys:
             - install4j-{{ checksum "scripts/extract-install4j.sh" }}
@@ -26,6 +28,8 @@ jobs:
       - restore_cache:
           key: dependency-cache
       - checkout
+      - run: git submodule sync
+      - run: git submodule update --init
       - restore_cache:
           key: install4j-{{ checksum "scripts/extract-install4j.sh" }}
       - run: scripts/extract-install4j.sh
@@ -47,6 +51,8 @@ jobs:
       - restore_cache:
           key: dependency-cache
       - checkout
+      - run: git submodule sync
+      - run: git submodule update --init
       - restore_cache:
           key: install4j-{{ checksum "scripts/extract-install4j.sh" }}
       - run: scripts/extract-install4j.sh
diff --git a/src/main/java/org/jabref/gui/util/ThemeLoader.java b/src/main/java/org/jabref/gui/util/ThemeLoader.java
index b2230505578..d7d452e2b3e 100644
--- a/src/main/java/org/jabref/gui/util/ThemeLoader.java
+++ b/src/main/java/org/jabref/gui/util/ThemeLoader.java
@@ -2,9 +2,9 @@
 
 import java.io.IOException;
 import java.net.MalformedURLException;
+import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.URL;
-import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Objects;
@@ -73,7 +73,6 @@ public ThemeLoader(FileUpdateMonitor fileUpdateMonitor, JabRefPreferences jabRef
         }
     }
 
-
     /**
      * Installs the base css file as a stylesheet in the given scene. Changes in the css file lead to a redraw of the
      * scene using the new css file.
@@ -89,18 +88,23 @@ private void addAndWatchForChanges(Scene scene, URL cssFile, int index) {
         scene.getStylesheets().add(index, cssFile.toExternalForm());
 
         try {
-            // If the file is an ordinary file (i.e. not a resource part of a .jar bundle), we watch it for changes and turn on live reloading
-            Path cssPath = Paths.get(cssFile.toURI());
-            if (Files.isRegularFile(cssPath)) {
-                LOGGER.info("Enabling live reloading of " + cssPath);
-                fileUpdateMonitor.addListenerForFile(cssPath, () -> {
-                    LOGGER.info("Reload css file " + cssFile);
-                    DefaultTaskExecutor.runInJavaFXThread(() -> {
-                        scene.getStylesheets().remove(cssFile.toExternalForm());
-                        scene.getStylesheets().add(index, cssFile.toExternalForm());
-                            }
-                    );
-                });
+
+            URI cssUri = cssFile.toURI();
+            if (!cssUri.toString().contains("jar")) {
+                LOGGER.debug("CSS URI {}", cssUri);
+
+                Path cssPath = Paths.get(cssUri).toAbsolutePath();
+                // If the file is an ordinary file (i.e. not a resource part of a .jar bundle), we watch it for changes and turn on live reloading
+                if (!cssUri.toString().contains("jar")) {
+                    LOGGER.info("Enabling live reloading of {}", cssPath);
+                    fileUpdateMonitor.addListenerForFile(cssPath, () -> {
+                        LOGGER.info("Reload css file " + cssFile);
+                        DefaultTaskExecutor.runInJavaFXThread(() -> {
+                            scene.getStylesheets().remove(cssFile.toExternalForm());
+                            scene.getStylesheets().add(index, cssFile.toExternalForm());
+                        });
+                    });
+                }
             }
         } catch (IOException | URISyntaxException e) {
             LOGGER.error("Could not watch css file for changes " + cssFile, e);