diff --git a/lib/fpm/package/deb.rb b/lib/fpm/package/deb.rb
index 342e6f43b8..55a9ac2fc9 100644
--- a/lib/fpm/package/deb.rb
+++ b/lib/fpm/package/deb.rb
@@ -17,7 +17,7 @@ class FPM::Package::Deb < FPM::Package
     :after_install      => "postinst",
     :before_remove      => "prerm",
     :after_remove       => "postrm",
-  }
+  } unless defined?(SCRIPT_MAP)
 
   option "--ignore-iteration-in-dependencies", :flag, 
             "For '=' (equal) dependencies, allow iterations on the specified " \
diff --git a/lib/fpm/package/rpm.rb b/lib/fpm/package/rpm.rb
index 7b9adaf8e4..f0a65fbc0a 100644
--- a/lib/fpm/package/rpm.rb
+++ b/lib/fpm/package/rpm.rb
@@ -21,13 +21,13 @@ class FPM::Package::RPM < FPM::Package
     "sha256" => 8,
     "sha384" => 9,
     "sha512" => 10
-  }
+  } unless defined?(DIGEST_ALGORITHM_MAP)
 
   COMPRESSION_MAP = {
     "xz" => "w2.xzdio",
     "gzip" => "w9.gzdio",
     "bzip2" => "w9.bzdio"
-  }
+  } unless defined?(COMPRESSION_MAP)
 
 
   option "--rpmbuild-define", "DEFINITION",