diff --git a/scripts/functions b/scripts/functions
index b71734b9..ec0d9a16 100644
--- a/scripts/functions
+++ b/scripts/functions
@@ -2149,8 +2149,7 @@ CT_DoExtractPatch()
         if [ -d "${overlay}" ]; then
             CT_DoExecLog ALL cp -av "${overlay}/." "${CT_BUILD_DIR}/overlay"
         else
-            ext=`CT_GetFileExtension "${overlay}"`
-            if [ ! -r "${overlay}${ext}" ]; then
+            if ! ext=`CT_GetFileExtension "${overlay}"`; then
                 CT_Abort "Overlay ${overlay} not found"
             fi
             CT_Extract "${overlay}${ext}" "${CT_BUILD_DIR}/overlay"