diff --git a/src/bin/common_trans.cc b/src/bin/common_trans.cc
index 919ce60af..c10adc014 100644
--- a/src/bin/common_trans.cc
+++ b/src/bin/common_trans.cc
@@ -425,6 +425,7 @@ static const argp_option options[] =
     { "%O,%D", 0, 0, OPTION_DOC | OPTION_NO_USAGE,
       "the automaton is output as either (%O) HOA/never claim/LBTT, or (%D) "
       "in LTL2DSTAR's format", 0 },
+    { "%%", 0, 0, OPTION_DOC | OPTION_NO_USAGE, "a single %", 0 },
     { 0, 0, 0, 0,
       "If either %l, %L, or %T are used, any input formula that does "
       "not use LBT-style atomic propositions (i.e. p0, p1, ...) will be "
diff --git a/src/tests/ltlcross3.test b/src/tests/ltlcross3.test
index 3dc9e9090..5bfa26ed5 100755
--- a/src/tests/ltlcross3.test
+++ b/src/tests/ltlcross3.test
@@ -161,6 +161,11 @@ test 5 = `wc -l < out.csv`
 check_csv out.csv
 
 
-# Diagnose empty automata
-run 1 ../../bin/ltlcross ': %f >%O' -f a 2>stderr
+# Diagnose empty automata, and make sure %% is correctly replaced by %
+run 1 ../../bin/ltlcross ': %f >%O; echo %%>foo' -f a 2>stderr
 test 2 = `grep -c 'error: empty output.' stderr`
+cat foo
+cat >expected<<EOF
+%
+EOF
+diff foo expected