diff --git a/src/common/sizer.cpp b/src/common/sizer.cpp
index 78ed8d2e39..380191d4e1 100644
--- a/src/common/sizer.cpp
+++ b/src/common/sizer.cpp
@@ -1406,6 +1406,18 @@ wxSizerItem *wxGridSizer::DoInsert(size_t index, wxSizerItem *item)
         }
     }
 
+    const int flags = item->GetFlag();
+    if ( flags & wxEXPAND )
+    {
+        // Check that expansion will happen in at least one of the directions.
+        wxASSERT_MSG
+        (
+            !(flags & (wxALIGN_BOTTOM | wxALIGN_CENTRE_VERTICAL)) ||
+                !(flags & (wxALIGN_RIGHT | wxALIGN_CENTRE_HORIZONTAL)),
+            wxS("wxEXPAND flag will be overridden by alignment flags")
+        );
+    }
+
     return wxSizer::DoInsert(index, item);
 }
 
diff --git a/tests/sizers/gridsizer.cpp b/tests/sizers/gridsizer.cpp
index f54e10567f..dd7b42fb01 100644
--- a/tests/sizers/gridsizer.cpp
+++ b/tests/sizers/gridsizer.cpp
@@ -39,9 +39,11 @@ public:
 private:
     CPPUNIT_TEST_SUITE( GridSizerTestCase );
         CPPUNIT_TEST( Expand );
+        CPPUNIT_TEST( IncompatibleFlags );
     CPPUNIT_TEST_SUITE_END();
 
     void Expand();
+    void IncompatibleFlags();
 
     // Clear the current sizer contents and add the specified windows to it,
     // using the same flags for all of them.
@@ -156,3 +158,12 @@ void GridSizerTestCase::Expand()
     CPPUNIT_ASSERT_EQUAL( wxSize(sizeChild.x, sizeRest.y),
                           children[3]->GetSize() );
 }
+
+void GridSizerTestCase::IncompatibleFlags()
+{
+    WX_ASSERT_FAILS_WITH_ASSERT_MESSAGE
+    (
+        "Combining wxEXPAND and wxCENTRE should assert",
+        m_sizer->Add(10, 10, wxSizerFlags().Expand().Centre())
+    );
+}