diff --git a/src/generic/gridsel.cpp b/src/generic/gridsel.cpp
index bd1652f25d..2d473c0ede 100644
--- a/src/generic/gridsel.cpp
+++ b/src/generic/gridsel.cpp
@@ -290,14 +290,15 @@ wxGridSelection::DeselectBlock(const wxGridBlockCoords& block,
             break;
         }
 
-        // remove the block
+        const wxGridBlockDiffResult result =
+            selBlock.Difference(canonicalizedBlock, splitOrientation);
+
+        // remove the block (note that selBlock, being a reference, is
+        // invalidated here and can't be used any more below)
         m_selection.erase(m_selection.begin() + n);
         n--;
         count--;
 
-        wxGridBlockDiffResult result =
-            selBlock.Difference(canonicalizedBlock, splitOrientation);
-
         for ( int i = 0; i < 2; ++i )
         {
             const wxGridBlockCoords& part = result.m_parts[i];