diff --git a/src/lib/eolian_cxx/grammar/inheritance_base_generator.hh b/src/lib/eolian_cxx/grammar/inheritance_base_generator.hh
index 82678496ee..38382d5092 100644
--- a/src/lib/eolian_cxx/grammar/inheritance_base_generator.hh
+++ b/src/lib/eolian_cxx/grammar/inheritance_base_generator.hh
@@ -21,7 +21,7 @@ _ns_as_prefix(eo_class const& cls)
    std::string::size_type found = s.find("::");
    while (found != std::string::npos)
      {
-        s.replace(found, 1, "_");
+        s.replace(found, 2, "_");
         found = s.find("::");
      }
    return s;