1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/yosys.h b/kernel/yosys.h
index 82eb069ab..c7b671724 100644
--- a/kernel/yosys.h
+++ b/kernel/yosys.h
@@ -244,7 +244,7 @@ extern bool memhasher_active;
 inline void memhasher() { if (memhasher_active) memhasher_do(); }
 
 void yosys_banner();
-int ceil_log2(int x);
+int ceil_log2(int x) YS_ATTRIBUTE(const);
 std::string stringf(const char *fmt, ...) YS_ATTRIBUTE(format(printf, 1, 2));
 std::string vstringf(const char *fmt, va_list ap);
 int readsome(std::istream &f, char *s, int n);