diff --git a/src/App/Document.cpp b/src/App/Document.cpp
index dc821048b2..cbdf1b23ab 100644
--- a/src/App/Document.cpp
+++ b/src/App/Document.cpp
@@ -2878,6 +2878,11 @@ void Document::renameObjectIdentifiers(
     }
 }
 
+void Document::setPreRecomputeHook(const PreRecomputeHook& hook)
+{
+     d->_preRecomputeHook = hook;
+}
+
 int Document::recompute(const std::vector<DocumentObject*>& objs,
                         bool force,
                         bool* hasError,
@@ -2918,7 +2923,13 @@ int Document::recompute(const std::vector<DocumentObject*>& objs,
     FC_TIME_INIT(t);
 
     Base::ObjectStatusLocker<Document::Status, Document> exe(Document::Recomputing, this);
-    signalBeforeRecompute(*this);
+
+    // This will hop into the main thread, fire signalBeforeRecompute(),
+    // and *block* the worker until the main thread is done, avoiding races
+    // between any running Python code and the rest of the recompute call.
+    if (d->_preRecomputeHook) {
+        d->_preRecomputeHook();
+    }
 
     //////////////////////////////////////////////////////////////////////////
     // FIXME Comment by Realthunder:
diff --git a/src/App/Document.h b/src/App/Document.h
index b78baa23f0..0c63005b58 100644
--- a/src/App/Document.h
+++ b/src/App/Document.h
@@ -193,6 +193,8 @@ public:
     //@}
     // NOLINTEND
 
+    using PreRecomputeHook = std::function<void()>;
+    void setPreRecomputeHook(const PreRecomputeHook& hook);
 
     void clearDocument();
 
diff --git a/src/App/private/DocumentP.h b/src/App/private/DocumentP.h
index eac25f6633..924a1c5430 100644
--- a/src/App/private/DocumentP.h
+++ b/src/App/private/DocumentP.h
@@ -98,6 +98,8 @@ struct DocumentP
 
     StringHasherRef Hasher {new StringHasher};
 
+    Document::PreRecomputeHook _preRecomputeHook;
+
     DocumentP();
 
     void addRecomputeLog(const char* why, App::DocumentObject* obj)
diff --git a/src/Gui/Document.cpp b/src/Gui/Document.cpp
index 2b0f171bf7..7182eaae31 100644
--- a/src/Gui/Document.cpp
+++ b/src/Gui/Document.cpp
@@ -39,6 +39,7 @@
 # include <QOpenGLWidget>
 # include <QTextStream>
 # include <QTimer>
+# include <QThread>
 # include <QStatusBar>
 # include <Inventor/actions/SoSearchAction.h>
 # include <Inventor/nodes/SoSeparator.h>
@@ -505,6 +506,8 @@ Document::Document(App::Document* pcDocument,Application * app)
         (std::bind(&Gui::Document::slotTransactionRemove, this, sp::_1, sp::_2));
     //NOLINTEND
 
+    pcDocument->setPreRecomputeHook([this] { callSignalBeforeRecompute(); });
+
     // pointer to the python class
     // NOTE: As this Python object doesn't get returned to the interpreter we
     // mustn't increment it (Werner Jan-12-2006)
@@ -1193,6 +1196,25 @@ void Document::slotTouchedObject(const App::DocumentObject &Obj)
     }
 }
 
+// helper that guarantees signalBeforeRecompute call is executed in the GUI thread and
+// that the worker waits until it finishes
+void Document::callSignalBeforeRecompute()
+{
+    auto invokeSignalBeforeRecompute = [this]{
+        // this runs in the GUI thread
+        this->getDocument()->signalBeforeRecompute(*this->getDocument());
+    };
+
+    if (QThread::currentThread() == qApp->thread()) {
+        // already on GUI thread – no hop, just call it
+        invokeSignalBeforeRecompute();
+    } else {
+        // hop to GUI and *block* until it returns
+        QMetaObject::invokeMethod(qApp, std::move(invokeSignalBeforeRecompute),
+                                  Qt::BlockingQueuedConnection);
+    }
+}
+
 void Document::addViewProvider(Gui::ViewProviderDocumentObject* vp)
 {
     // Hint: The undo/redo first adds the view provider to the Gui
diff --git a/src/Gui/Document.h b/src/Gui/Document.h
index 4852f6bcd6..ae27120a6b 100644
--- a/src/Gui/Document.h
+++ b/src/Gui/Document.h
@@ -94,6 +94,7 @@ protected:
     void slotSkipRecompute(const App::Document &doc, const std::vector<App::DocumentObject*> &objs);
     void slotTouchedObject(const App::DocumentObject &);
     void slotChangePropertyEditor(const App::Document&, const App::Property &);
+    void callSignalBeforeRecompute();
     //@}
 
 public: