diff --git a/passes/pmgen/test_pmgen.cc b/passes/pmgen/test_pmgen.cc
index 5b0cf0751..2695fe802 100644
--- a/passes/pmgen/test_pmgen.cc
+++ b/passes/pmgen/test_pmgen.cc
@@ -217,7 +217,7 @@ void generate_pattern(std::function<void(pm&,std::function<void()>)> run, const
 			run(matcher, [](){});
 		}
 
-		if (submodcnt)
+		if (submodcnt && maxsubcnt < (1 << 16))
 			maxsubcnt *= 2;
 
 		design->remove(mod);