diff --git a/src/gtk/textctrl.cpp b/src/gtk/textctrl.cpp
index 255544eeda..2495c498df 100644
--- a/src/gtk/textctrl.cpp
+++ b/src/gtk/textctrl.cpp
@@ -1198,13 +1198,29 @@ long wxTextCtrl::XYToPosition(long x, long y ) const
         return x;
     }
 
+    const gint numLines = gtk_text_buffer_get_line_count (m_buffer);
+
     GtkTextIter iter;
-    if (y >= gtk_text_buffer_get_line_count (m_buffer))
+    if (y >= numLines)
         return -1;
 
     gtk_text_buffer_get_iter_at_line(m_buffer, &iter, y);
-    if (x >= gtk_text_iter_get_chars_in_line (&iter))
+
+    const gint lineLength = gtk_text_iter_get_chars_in_line (&iter);
+    if (x > lineLength)
+    {
+        // This coordinate is always invalid.
         return -1;
+    }
+
+    if (x == lineLength)
+    {
+        // In this case the coordinate is considered to be valid by wx if this
+        // is the last line, as it corresponds to the last position beyond the
+        // last character of the text, and invalid otherwise.
+        if (y != numLines - 1)
+            return -1;
+    }
 
     return gtk_text_iter_get_offset(&iter) + x;
 }
diff --git a/tests/controls/textctrltest.cpp b/tests/controls/textctrltest.cpp
index 175d46d011..89ff430cd3 100644
--- a/tests/controls/textctrltest.cpp
+++ b/tests/controls/textctrltest.cpp
@@ -935,6 +935,7 @@ void TextCtrlTestCase::DoXYToPositionMultiLine(long style)
         for( long x = 0; x < maxLineLength_0+1; x++ )
         {
             long p = m_text->XYToPosition(x, y);
+            INFO("x=" << x << ", y=" << y);
             CPPUNIT_ASSERT_EQUAL( pos_0[y][x], p );
         }
 
@@ -951,6 +952,7 @@ void TextCtrlTestCase::DoXYToPositionMultiLine(long style)
         for( long x = 0; x < maxLineLength_1+1; x++ )
         {
             long p = m_text->XYToPosition(x, y);
+            INFO("x=" << x << ", y=" << y);
             CPPUNIT_ASSERT_EQUAL( pos_1[y][x], p  );
         }
 
@@ -985,6 +987,7 @@ void TextCtrlTestCase::DoXYToPositionMultiLine(long style)
         for( long x = 0; x < maxLineLength_2+1; x++ )
         {
             long p = m_text->XYToPosition(x, y);
+            INFO("x=" << x << ", y=" << y);
             CPPUNIT_ASSERT_EQUAL( ref_pos_2[y][x], p );
         }
 
@@ -1021,6 +1024,7 @@ void TextCtrlTestCase::DoXYToPositionMultiLine(long style)
         for( long x = 0; x < maxLineLength_3+1; x++ )
         {
             long p = m_text->XYToPosition(x, y);
+            INFO("x=" << x << ", y=" << y);
             CPPUNIT_ASSERT_EQUAL( ref_pos_3[y][x], p );
         }
 
@@ -1061,6 +1065,7 @@ void TextCtrlTestCase::DoXYToPositionMultiLine(long style)
         for( long x = 0; x < maxLineLength_4+1; x++ )
         {
             long p = m_text->XYToPosition(x, y);
+            INFO("x=" << x << ", y=" << y);
             CPPUNIT_ASSERT_EQUAL( ref_pos_4[y][x], p );
         }
 }