Add const.

1 files changed, 1 insertions, 1 deletions

diff --git a/c/pl.h b/c/pl.h
index 44b8a5e..d1c01c4 100644
--- a/c/pl.h
+++ b/c/pl.h
@@ -111,7 +111,7 @@ int Pl(const char* const szMod, const char* const szPred, T... xs)
 {
 	try {
 		return Plx(szMod, szPred, xs...);
-	} catch (term_t& t) {
+	} catch (const term_t& t) {
 		return 0;
 	}
 }