diff --git a/src/common/cmdline.cpp b/src/common/cmdline.cpp
index 5ac040b271..2c5ea56421 100644
--- a/src/common/cmdline.cpp
+++ b/src/common/cmdline.cpp
@@ -460,6 +460,8 @@ size_t wxCmdLineParser::GetParamCount() const
 
 wxString wxCmdLineParser::GetParam(size_t n) const
 {
+    wxCHECK_MSG( n < GetParamCount(), wxEmptyString, _T("invalid param index") );
+
     return m_data->m_parameters[n];
 }