diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index 46ccbae0..f6d4dab0 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -998,7 +998,7 @@ String dump_regex(const CompiledRegex& program)
     int count = 0;
     for (auto& inst : program.instructions)
     {
-        char buf[10];
+        char buf[20];
         sprintf(buf, " %03d     ", count++);
         res += buf;
         switch (inst.op)