diff --git a/common/richio.cpp b/common/richio.cpp
index a4e40087cb..3791e44566 100644
--- a/common/richio.cpp
+++ b/common/richio.cpp
@@ -71,9 +71,11 @@ void LINE_READER::expandCapacity( unsigned newsize )
         // resize the buffer, and copy the original data
         char* bigger = new char[capacity];
 
+        wxASSERT( capacity >= length );
+
         memcpy( bigger, line, length );
 
-        delete line;
+        delete[] line;
         line = bigger;
     }
 }