diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index 9ddcc655d8ca..0e6a036404e4 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,18 @@
+2017-08-10  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        [GTK] Crashes in WebCore::PasteboardHelper::fillSelectionData when source file of drag is unavailable
+        https://bugs.webkit.org/show_bug.cgi?id=174161
+
+        Reviewed by Xabier Rodriguez-Calvar.
+
+        In r219385 we changed the early return in fillSelectionData() to check the selection data length instead of the
+        data pointer. However, the gtk_selection_data_get_length() can return -1, so we need to check also if the value
+        less than 0. The case of setting an empty string could be valid depending on the target type, so it's better to
+        return early only when data lenght is less than 0 and handle the 0 length case in each target.
+
+        * platform/gtk/PasteboardHelper.cpp:
+        (WebCore::PasteboardHelper::fillSelectionData):
+
 2017-08-10  Antti Koivisto  <antti@apple.com>
 
         Text renderer updates should be done by RenderTreeUpdater
diff --git a/Source/WebCore/platform/gtk/PasteboardHelper.cpp b/Source/WebCore/platform/gtk/PasteboardHelper.cpp
index eeb7cf76868a..d251e6892749 100644
--- a/Source/WebCore/platform/gtk/PasteboardHelper.cpp
+++ b/Source/WebCore/platform/gtk/PasteboardHelper.cpp
@@ -209,7 +209,7 @@ void PasteboardHelper::fillSelectionData(const SelectionData& selection, unsigne
 
 void PasteboardHelper::fillSelectionData(GtkSelectionData* data, unsigned /* info */, SelectionData& selection)
 {
-    if (!gtk_selection_data_get_length(data))
+    if (gtk_selection_data_get_length(data) < 0)
         return;
 
     GdkAtom target = gtk_selection_data_get_target(data);
@@ -228,11 +228,11 @@ void PasteboardHelper::fillSelectionData(GtkSelectionData* data, unsigned /* inf
 
         // Give preference to text/uri-list here, as it can hold more
         // than one URI but still take  the label if there is one.
-        if (!selection.hasURIList())
+        if (!selection.hasURIList() && !pieces.isEmpty())
             selection.setURIList(pieces[0]);
         if (pieces.size() > 1)
             selection.setText(pieces[1]);
-    } else if (target == unknownAtom) {
+    } else if (target == unknownAtom && gtk_selection_data_get_length(data)) {
         GRefPtr<GVariant> variant = g_variant_new_parsed(reinterpret_cast<const char*>(gtk_selection_data_get_data(data)));
 
         GUniqueOutPtr<gchar> key;