diff --git a/development/cmake/modules/LyXMacros.cmake b/development/cmake/modules/LyXMacros.cmake
index cdcbae809d..ff0822e32a 100644
--- a/development/cmake/modules/LyXMacros.cmake
+++ b/development/cmake/modules/LyXMacros.cmake
@@ -266,7 +266,7 @@ macro(LYX_STRING _name _description _default)
     if (NOT "${tmp_lyx_name}" MATCHES "^\\..*$")
       set(tmp_lyx_name ".${tmp_lyx_name}")
     endif()
-    if (NOT "${tmp_lyx_name}" MATCHES "^\\.[a-zA-Z_\\.]+$")
+    if (NOT "${tmp_lyx_name}" MATCHES "^\\.[a-zA-Z_0-9\\.]+$")
       message(FATAL_ERROR "Invalid string for lyx suffix (${tmp_lyx_name})")
     endif()
   endif()