diff --git a/src/format_tptp.rs b/src/format_tptp.rs
index a53bd59..62dd832 100644
--- a/src/format_tptp.rs
+++ b/src/format_tptp.rs
@@ -524,12 +524,14 @@ impl<'a> std::fmt::Debug for FormulaDisplay<'a>
 					{
 						let argument_is_arithmetic_term = is_arithmetic_term(argument);
 
+						write!(format, "{}", separator)?;
+
 						if argument_is_arithmetic_term
 						{
 							write!(format, "f__integer__(")?;
 						}
 
-						write!(format, "{}{:?}", separator, argument.display_tptp())?;
+						write!(format, "{:?}", argument.display_tptp())?;
 
 						if argument_is_arithmetic_term
 						{