diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
index fbbe2373f..eab5bb3d1 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
@@ -614,7 +614,7 @@ struct value : public expr_base<value<Bits>> {
 		int64_t divisor_shift = divisor.ctlz() - dividend.ctlz();
 		assert(divisor_shift >= 0);
 		divisor = divisor.shl(value<Bits>{(chunk::type) divisor_shift});
-		for (size_t step = 0; step <= divisor_shift; step++) {
+		for (size_t step = 0; step <= (uint64_t) divisor_shift; step++) {
 			quotient = quotient.shl(value<Bits>{1u});
 			if (!dividend.ucmp(divisor)) {
 				dividend = dividend.sub(divisor);