diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
index 04ed48eb3..2d5451287 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
@@ -583,8 +583,9 @@ struct value : public expr_base<value<Bits>> {
 		value<Bits> dividend = *this;
 		if (dividend.ucmp(divisor))
 			return {/*quotient=*/value<Bits>{0u}, /*remainder=*/dividend};
-		uint32_t divisor_shift = divisor.ctlz() - dividend.ctlz();
-		divisor = divisor.shl(value<Bits>{divisor_shift});
+		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++) {
 			quotient = quotient.shl(value<Bits>{1u});
 			if (!dividend.ucmp(divisor)) {