diff --git a/jsonchecker/fail62.json b/jsonchecker/fail62.json
new file mode 100644
index 000000000..0b2d0bbe7
--- /dev/null
+++ b/jsonchecker/fail62.json
@@ -0,0 +1 @@
+{"foo":"baa}
diff --git a/jsonchecker/fail63.json b/jsonchecker/fail63.json
new file mode 100644
index 000000000..a36de6d48
--- /dev/null
+++ b/jsonchecker/fail63.json
@@ -0,0 +1 @@
+"f[
diff --git a/jsonchecker/fail64.json b/jsonchecker/fail64.json
new file mode 100644
index 000000000..1cc80efa6
--- /dev/null
+++ b/jsonchecker/fail64.json
@@ -0,0 +1 @@
+"
diff --git a/src/stage1_find_marks.cpp b/src/stage1_find_marks.cpp
index d764aa042..369b53714 100644
--- a/src/stage1_find_marks.cpp
+++ b/src/stage1_find_marks.cpp
@@ -609,6 +609,12 @@ WARN_UNUSED
                                        quote_bits, prev_iter_ends_pseudo_pred);
     idx += 64;
   }
+
+  // is last string quote closed?
+  if (prev_iter_inside_quote) {
+      return false;
+  }
+
   // finally, flatten out the remaining structurals from the last iteration
   flatten_bits(base_ptr, base, idx, structurals);