diff --git a/polymer/eduke32/build/src/build.c b/polymer/eduke32/build/src/build.c
index b5eb70f78..e3751050c 100644
--- a/polymer/eduke32/build/src/build.c
+++ b/polymer/eduke32/build/src/build.c
@@ -496,10 +496,11 @@ int32_t app_main(int32_t argc, const char **argv)
             }
             continue;
         }
+
         if (!boardfilename[0])
         {
             Bstrncpy(boardfilename, argv[i], BMAX_PATH);
-            boardfilename[i-BMAX_PATH] = 0;
+            boardfilename[BMAX_PATH-1] = 0;
         }
     }
     if (boardfilename[0] == 0)