diff --git a/src/msw/crashrpt.cpp b/src/msw/crashrpt.cpp
index 10996846cd..7098089b5e 100644
--- a/src/msw/crashrpt.cpp
+++ b/src/msw/crashrpt.cpp
@@ -1118,7 +1118,7 @@ bool wxHandleFatalExceptions(bool doit)
                          );
 
         wxStrncat(gs_reportFilename, fname,
-                  WXSIZEOF(gs_reportFilename) - strlen(gs_reportFilename) - 1);
+                  WXSIZEOF(gs_reportFilename) - wxStrlen(gs_reportFilename) - 1);
     }
 
     return true;