diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -150,6 +150,7 @@
  Qt5::Xml                   # davjob.cpp uses QDom
  KF5::I18n
  KF5::DBusAddons            # KDEInitInterface
+ KF5::WidgetsAddons
 )
 
 if (UNIX)
diff --git a/src/core/copyjob.cpp b/src/core/copyjob.cpp
--- a/src/core/copyjob.cpp
+++ b/src/core/copyjob.cpp
@@ -46,6 +46,8 @@
 
 #include <kdirnotify.h>
 
+#include <kmessagebox.h>
+
 #ifdef Q_OS_UNIX
 #include <utime.h>
 #endif
@@ -884,7 +886,35 @@
         slotReport();
 
         qCDebug(KIO_COPYJOB_DEBUG)<<"Stating finished. To copy:"<<m_totalSize<<", available:"<<m_freeSpace;
-        //TODO warn user beforehand if space is not enough
+
+        if (m_totalSize > m_freeSpace) {
+            SimpleJobPrivate *sjp;
+            int msgRes;
+            msgRes = sjp->requestMessageBox(JobUiDelegateExtension::WarningYesNo,
+                                            QString("Warning!"),
+                                            QString("Yes"),
+                                            QString("No"),
+                                            i18n("You do not have sufficient space available at %1 (%2 required but only %3 available)."
+                                                 "Do you still want to continue?",
+                                                  m_dest.path(),
+                                                  KIO::convertSize(m_totalSize),
+                                                  KIO::convertSize(m_freeSpace)
+                                                ),
+                                            QString(),
+                                            QString(),
+                                            QString(),
+                                            KIO::MetaData()
+                                           );
+
+            if (msgRes == KMessageBox::Yes) {
+                goto yes;
+            } else {
+                return;
+            }
+
+        }
+
+        yes:
 
         if (!dirs.isEmpty()) {
             emit q->aboutToCreate(q, dirs);