diff --git a/src/util/util.h b/src/util/util.h
index 189629e7f2..ae39e96a37 100644
--- a/src/util/util.h
+++ b/src/util/util.h
@@ -103,9 +103,9 @@ static inline unsigned next_power_of_two(unsigned v) {
 /**
    \brief Return the position of the most significant bit.
 */
-static inline unsigned log2(int v) { return std::bit_width((unsigned)v) - 1; }
-static inline unsigned log2(unsigned v) { return std::bit_width(v) - 1; }
-static inline unsigned log2(uint64_t v) { return std::bit_width(v) - 1; }
+static inline unsigned log2(int v) { return v > 0 ? (std::bit_width(static_cast<unsigned>(v)) - 1) : 0; }
+static inline unsigned log2(unsigned v) { return v ? (std::bit_width(v) - 1) : 0; }
+static inline unsigned log2(uint64_t v) { return v ? (std::bit_width(v) - 1) : 0; }
 
 static_assert(sizeof(unsigned) == 4, "unsigned are 32 bits");