diff --git a/kernel/hashlib.h b/kernel/hashlib.h
index 6927702e1..188b176b4 100644
--- a/kernel/hashlib.h
+++ b/kernel/hashlib.h
@@ -324,10 +324,10 @@ template<typename T> struct hash_ops<std::optional<T>> {
 	}
 };
 
-inline int hashtable_size(int min_size)
+inline unsigned int hashtable_size(unsigned int min_size)
 {
 	// Primes as generated by https://oeis.org/A175953
-	static std::vector<int> zero_and_some_primes = {
+	static std::vector<unsigned int> zero_and_some_primes = {
 		0, 23, 29, 37, 47, 59, 79, 101, 127, 163, 211, 269, 337, 431, 541, 677,
 		853, 1069, 1361, 1709, 2137, 2677, 3347, 4201, 5261, 6577, 8231, 10289,
 		12889, 16127, 20161, 25219, 31531, 39419, 49277, 61603, 77017, 96281,
@@ -337,13 +337,13 @@ inline int hashtable_size(int min_size)
 		25499291, 31874149, 39842687, 49803361, 62254207, 77817767, 97272239,
 		121590311, 151987889, 189984863, 237481091, 296851369, 371064217,
 		463830313, 579787991, 724735009, 905918777, 1132398479, 1415498113,
-		1769372713
+		1769372713, 2211715897, 2764644887, 3455806139
 	};
 
 	for (auto p : zero_and_some_primes)
 		if (p >= min_size) return p;
 
-	if (sizeof(int) == 4)
+	if (sizeof(unsigned int) == 4)
 		throw std::length_error("hash table exceeded maximum size.\nDesign is likely too large for yosys to handle, if possible try not to flatten the design.");
 
 	for (auto p : zero_and_some_primes)