diff --git a/test/tools/ossfuzz/SolidityGenerator.cpp b/test/tools/ossfuzz/SolidityGenerator.cpp
index 52c35513e..03dc5c97e 100644
--- a/test/tools/ossfuzz/SolidityGenerator.cpp
+++ b/test/tools/ossfuzz/SolidityGenerator.cpp
@@ -303,7 +303,9 @@ string BlockStmtGenerator::visit()
 		return "\n";
 	incrementNestingDepth();
 	ostringstream block;
-	block << indentation() + "{\n";
+	// Make block unchecked with a small probability
+	bool unchecked = uRandDist->probable(s_uncheckedInvProb);
+	block << indentation() + (unchecked ? "unchecked " : "") + "{\n";
 	state->indent();
 	block << visitChildren();
 	state->unindent();
diff --git a/test/tools/ossfuzz/SolidityGenerator.h b/test/tools/ossfuzz/SolidityGenerator.h
index 5fd4a6488..68e48bdba 100644
--- a/test/tools/ossfuzz/SolidityGenerator.h
+++ b/test/tools/ossfuzz/SolidityGenerator.h
@@ -876,6 +876,7 @@ private:
 	size_t m_nestingDepth;
 	static constexpr unsigned s_maxStatements = 4;
 	static constexpr unsigned s_maxNestingDepth = 3;
+	static constexpr size_t s_uncheckedInvProb = 13;
 };
 
 class SolidityGenerator: public std::enable_shared_from_this<SolidityGenerator>