diff --git a/src/library/blast/expr.cpp b/src/library/blast/expr.cpp
index 14b462d42..dbb2feb0e 100644
--- a/src/library/blast/expr.cpp
+++ b/src/library/blast/expr.cpp
@@ -121,11 +121,18 @@ scope_hash_consing::~scope_hash_consing() {
     g_lref_array  = reinterpret_cast<expr_array*>(m_lref_array);
 }
 
+#ifdef LEAN_DEBUG
 static bool is_cached(level const & l) {
     lean_assert(g_level_table);
     return g_level_table->find(l) != g_level_table->end();
 }
 
+static bool is_cached(expr const & l) {
+    lean_assert(g_expr_table);
+    return g_expr_table->find(l) != g_expr_table->end();
+}
+#endif
+
 static level cache(level const & l) {
     lean_assert(g_level_table);
     auto r = g_level_table->find(l);
@@ -135,11 +142,6 @@ static level cache(level const & l) {
     return l;
 }
 
-static bool is_cached(expr const & l) {
-    lean_assert(g_expr_table);
-    return g_expr_table->find(l) != g_expr_table->end();
-}
-
 static expr cache(expr const & e) {
     lean_assert(g_expr_table);
     auto r = g_expr_table->find(e);