diff --git a/cpp/ql/src/experimental/parsing/glr.qll b/cpp/ql/src/experimental/parsing/glr.qll
index 39ce4243a7a..f3cef9977d8 100644
--- a/cpp/ql/src/experimental/parsing/glr.qll
+++ b/cpp/ql/src/experimental/parsing/glr.qll
@@ -426,11 +426,16 @@ module GLR<grammar/0 g> {
       result = "There are " + sr + " shift/reduce conflicts and " + rr + " reduce/reduce conflicts."
     )
   }
+
+  // This should be empty
+  predicate debugStates(State state1, Symbol s) {
+    count(state1.getTransition(s))>1
+  }
 }
 
 // Just some debugging information needed to quickeval predicates in modules
-string test_input(int i) { result = "I+I".charAt(i) }
+string test_input(int i) { result = "I+I-I".charAt(i) }
 
-string test_grammar() { result = ["G -> E", "E -> E + E", "E -> I"] }
+string test_grammar() { result = ["G -> E", "E -> E + I", "E -> E - I", "E -> I"] }
 
 module DebugContext = GLR<test_grammar/0>::GLRparser<test_input/1>;
diff --git a/cpp/ql/src/experimental/parsing/test4.ql b/cpp/ql/src/experimental/parsing/test4.ql
new file mode 100644
index 00000000000..9d34e88c1c1
--- /dev/null
+++ b/cpp/ql/src/experimental/parsing/test4.ql
@@ -0,0 +1,17 @@
+import glr
+
+string grammar4() {
+    result = ["G -> E", "E -> E + I", "E -> E - I", "E -> I"]
+}
+
+string input4(int i) { result = "I+I-I".charAt(i) }
+
+module Test4 = GLR<grammar4/0>::GLRparser<input4/1>;
+
+query string conflicts() { result = GLR<grammar4/0>::conflicts() }
+
+query int syntax_error() { result = Test4::syntax_error_position() }
+
+from Test4::ParseNode parent, int i, Test4::ParseNode child
+where Test4::tree(parent,i,child)
+select parent, i, child