diff --git a/passes/techmap/alumacc.cc b/passes/techmap/alumacc.cc
index 2a1fcb9f9..29ec094b4 100644
--- a/passes/techmap/alumacc.cc
+++ b/passes/techmap/alumacc.cc
@@ -380,7 +380,10 @@ struct AlumaccWorker
 			alunode->c = C;
 			alunode->y = n->y;
 
-			sig_alu[RTLIL::SigSig(A, B)].insert(alunode);
+			// only consider merging if the output is at least as wide as the inputs
+			if (max(GetSize(A), GetSize(B)) <= GetSize(n->y)) {
+				sig_alu[RTLIL::SigSig(A, B)].insert(alunode);
+			}
 			delete_nodes.insert(n);
 		next_macc:;
 		}
@@ -432,10 +435,6 @@ struct AlumaccWorker
 				// comparators need subtraction
 				return false;
 			}
-			if (max(GetSize(cmp_A), GetSize(cmp_B)) > GetSize(node->y)) {
-				// must have at least as many output bits
-				return false;
-			}
 			if (is_signed != node->is_signed) {
 				if (GetSize(cmp_A) != GetSize(cmp_B)) {
 					// mismatched input widths are problematic when mixing signedness