diff --git a/QtAV.pro b/QtAV.pro
index d7b3853e..1d42e659 100644
--- a/QtAV.pro
+++ b/QtAV.pro
@@ -51,7 +51,7 @@ greaterThan(QT_MAJOR_VERSION, 5) {
     message("cache: $$_QMAKE_CACHE_QT4_")
 }
 cache(BUILD_DIR, set, BUILD_DIR)
-cache(BUILD_ROOT, set, BUILD_DIR)
+#cache(BUILD_ROOT, set, BUILD_DIR)
 cache(SOURCE_ROOT, set, SOURCE_ROOT)
 cache(mkspecs_cached, set, mkspecs_build)
 
diff --git a/configure.prf b/configure.prf
index 08c1fec1..51cad67a 100644
--- a/configure.prf
+++ b/configure.prf
@@ -46,7 +46,9 @@ defineTest(cache) {
 #use sed for unix or msys
 #convert '/' to '\/' for sed
         srcval ~= s,/,\/,g
-        system("sed -i '/$${srcval}/d' $$_QMAKE_CACHE_QT4_ >/dev/null")
+        srcval ~= s,\+,\\+,g #for sed regexp. '+' in qmake is '\+' ?
+        system("sed -i -r '/.*$${dstvar}.*$${srcval}.*/d' $$_QMAKE_CACHE_QT4_ >/dev/null")
+        message("sed -i -r '/.*$${dstvar}.*$${srcval}.*/d' $$_QMAKE_CACHE_QT4_ >/dev/null")
     }
     write_file($$_QMAKE_CACHE_QT4_, varstr, append)
 }