diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1a75af1b603..e62873f5eed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -62,6 +62,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - The "Automatically set file links" feature now follows symbolic links. [#5664](https://github.com/JabRef/jabref/issues/5664)
 - After successful import of one or multiple bib entries the main table scrolls to the first imported entry [#5383](https://github.com/JabRef/jabref/issues/5383)
 - We fixed an exception which occurred when an invalid jstyle was loaded. [#5452](https://github.com/JabRef/jabref/issues/5452)
+- We fixed an issue where the command line arguments `importBibtex` and `importToOpen` did not import into the currently open library, but opened a new one. [#5537](https://github.com/JabRef/jabref/issues/5537)
 - We fixed an error where the preview theme did not adapt to the "Dark" mode [#5463](https://github.com/JabRef/jabref/issues/5463)
 - We fixed an issue where the merge dialog showed the wrong text colour in "Dark" mode [#5516](https://github.com/JabRef/jabref/issues/5516)
 - We fixed visibility issues with the scrollbar and group selection highlight in "Dark" mode, and enabled "Dark" mode for the OpenOffice preview in the style selection window. [#5522](https://github.com/JabRef/jabref/issues/5522)
diff --git a/src/main/java/org/jabref/JabRefGUI.java b/src/main/java/org/jabref/JabRefGUI.java
index e5070ca912b..4ddd788eff9 100644
--- a/src/main/java/org/jabref/JabRefGUI.java
+++ b/src/main/java/org/jabref/JabRefGUI.java
@@ -3,8 +3,8 @@
 import java.io.File;
 import java.sql.SQLException;
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import javafx.application.Platform;
 import javafx.scene.Scene;
@@ -97,6 +97,13 @@ private void openDatabases() {
             openLastEditedDatabases();
         }
 
+        // Remove invalid databases
+        List<ParserResult> invalidDatabases = bibDatabases.stream()
+                                                          .filter(ParserResult::isInvalid)
+                                                          .collect(Collectors.toList());
+        failed.addAll(invalidDatabases);
+        bibDatabases.removeAll(invalidDatabases);
+
         // passed file (we take the first one) should be focused
         String focusedFile = bibDatabases.stream()
                                          .findFirst()
@@ -106,40 +113,34 @@ private void openDatabases() {
 
         // Add all bibDatabases databases to the frame:
         boolean first = false;
-        if (!bibDatabases.isEmpty()) {
-            for (Iterator<ParserResult> parserResultIterator = bibDatabases.iterator(); parserResultIterator.hasNext();) {
-                ParserResult pr = parserResultIterator.next();
-                // Define focused tab
-                if (pr.getFile().filter(path -> path.getAbsolutePath().equals(focusedFile)).isPresent()) {
-                    first = true;
-                }
+        for (ParserResult pr : bibDatabases) {
+            // Define focused tab
+            if (pr.getFile().filter(path -> path.getAbsolutePath().equals(focusedFile)).isPresent()) {
+                first = true;
+            }
 
-                if (pr.isInvalid()) {
-                    failed.add(pr);
-                    parserResultIterator.remove();
-                } else if (pr.getDatabase().isShared()) {
-                    try {
-                        new SharedDatabaseUIManager(mainFrame).openSharedDatabaseFromParserResult(pr);
-                    } catch (SQLException | DatabaseNotSupportedException | InvalidDBMSConnectionPropertiesException |
-                            NotASharedDatabaseException e) {
-                        pr.getDatabaseContext().clearDatabaseFile(); // do not open the original file
-                        pr.getDatabase().clearSharedDatabaseID();
-
-                        LOGGER.error("Connection error", e);
-                        mainFrame.getDialogService().showErrorDialogAndWait(
-                                Localization.lang("Connection error"),
-                                Localization.lang("A local copy will be opened."),
-                                e);
-                    }
-                    toOpenTab.add(pr);
-                } else if (pr.toOpenTab()) {
-                    // things to be appended to an opened tab should be done after opening all tabs
-                    // add them to the list
-                    toOpenTab.add(pr);
-                } else {
-                    mainFrame.addParserResult(pr, first);
-                    first = false;
+            if (pr.getDatabase().isShared()) {
+                try {
+                    new SharedDatabaseUIManager(mainFrame).openSharedDatabaseFromParserResult(pr);
+                } catch (SQLException | DatabaseNotSupportedException | InvalidDBMSConnectionPropertiesException |
+                        NotASharedDatabaseException e) {
+                    pr.getDatabaseContext().clearDatabaseFile(); // do not open the original file
+                    pr.getDatabase().clearSharedDatabaseID();
+
+                    LOGGER.error("Connection error", e);
+                    mainFrame.getDialogService().showErrorDialogAndWait(
+                            Localization.lang("Connection error"),
+                            Localization.lang("A local copy will be opened."),
+                            e);
                 }
+                toOpenTab.add(pr);
+            } else if (pr.toOpenTab()) {
+                // things to be appended to an opened tab should be done after opening all tabs
+                // add them to the list
+                toOpenTab.add(pr);
+            } else {
+                mainFrame.addParserResult(pr, first);
+                first = false;
             }
         }
 
diff --git a/src/main/java/org/jabref/gui/JabRefFrame.java b/src/main/java/org/jabref/gui/JabRefFrame.java
index 39c5c3c72b3..541da4646e2 100644
--- a/src/main/java/org/jabref/gui/JabRefFrame.java
+++ b/src/main/java/org/jabref/gui/JabRefFrame.java
@@ -972,37 +972,35 @@ public void updateAllTabTitles() {
     }
 
     public void addTab(BasePanel basePanel, boolean raisePanel) {
-        DefaultTaskExecutor.runInJavaFXThread(() -> {
-            // add tab
-            Tab newTab = new Tab(basePanel.getTabTitle(), basePanel);
-            tabbedPane.getTabs().add(newTab);
-            newTab.setOnCloseRequest(event -> {
-                closeTab((BasePanel) newTab.getContent());
-                event.consume();
-            });
+        // add tab
+        Tab newTab = new Tab(basePanel.getTabTitle(), basePanel);
+        tabbedPane.getTabs().add(newTab);
+        newTab.setOnCloseRequest(event -> {
+            closeTab((BasePanel) newTab.getContent());
+            event.consume();
+        });
 
-            // update all tab titles
-            updateAllTabTitles();
+        // update all tab titles
+        updateAllTabTitles();
 
-            if (raisePanel) {
-                tabbedPane.getSelectionModel().select(newTab);
-            }
+        if (raisePanel) {
+            tabbedPane.getSelectionModel().select(newTab);
+        }
 
-            // Register undo/redo listener
-            basePanel.getUndoManager().registerListener(new UndoRedoEventManager());
+        // Register undo/redo listener
+        basePanel.getUndoManager().registerListener(new UndoRedoEventManager());
 
-            BibDatabaseContext context = basePanel.getBibDatabaseContext();
+        BibDatabaseContext context = basePanel.getBibDatabaseContext();
 
-            if (readyForAutosave(context)) {
-                AutosaveManager autosaver = AutosaveManager.start(context);
-                autosaver.registerListener(new AutosaveUIManager(basePanel));
-            }
+        if (readyForAutosave(context)) {
+            AutosaveManager autosaver = AutosaveManager.start(context);
+            autosaver.registerListener(new AutosaveUIManager(basePanel));
+        }
 
-            BackupManager.start(context, Globals.entryTypesManager, prefs);
+        BackupManager.start(context, Globals.entryTypesManager, prefs);
 
-            // Track opening
-            trackOpenNewDatabase(basePanel);
-        });
+        // Track opening
+        trackOpenNewDatabase(basePanel);
     }
 
     private void trackOpenNewDatabase(BasePanel basePanel) {