diff --git a/.gitignore b/.gitignore
index 319d66928..415bb9372 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,3 +25,4 @@ src/exp
 src/user/CylindricalDisk.cc
 src/user/EllipsoidForce.cc
 src/user/SLSphere.cc
+_codeql_build_dir
diff --git a/_codeql_detected_source_root b/_codeql_detected_source_root
new file mode 120000
index 000000000..945c9b46d
--- /dev/null
+++ b/_codeql_detected_source_root
@@ -0,0 +1 @@
+.
\ No newline at end of file
diff --git a/exputil/ExpDeproj.cc b/exputil/ExpDeproj.cc
index 4e6a66b76..183711d6d 100644
--- a/exputil/ExpDeproj.cc
+++ b/exputil/ExpDeproj.cc
@@ -12,8 +12,8 @@
 
 void ExpDeproj::initialize()
 {
-  if (ngrid <= 0) {
-    throw std::invalid_argument("n must be positive");
+  if (ngrid < 2) {
+    throw std::invalid_argument("n must be at least 2");
   }
 
   rv.resize(ngrid);