diff --git a/include/openmc/file_utils.h b/include/openmc/file_utils.h
index f9c23468d..ae3a26e94 100644
--- a/include/openmc/file_utils.h
+++ b/include/openmc/file_utils.h
@@ -3,15 +3,31 @@
 
 #include <fstream> // for ifstream
 #include <string>
+#include <sys/stat.h>
 
 namespace openmc {
 
+// TODO: replace with std::filesysem when switch to C++17 is made
+//! Determine if a path is a directory
+//! \param[in] path Path to check
+//! \return Whether the path is a directory
+inline bool is_dir(const std::string& path) {
+  struct stat s;
+  if (stat(path.c_str(), &s) != 0) return false;
+
+  return s.st_mode & S_IFDIR;
+}
+
 //! Determine if a file exists
 //! \param[in] filename Path to file
 //! \return Whether file exists
 inline bool file_exists(const std::string& filename)
 {
+  // rule out file being a directory path
+  if (is_dir(filename)) return false;
+
   std::ifstream s {filename};
+  s.seekg(0, std::ios::beg);
   return s.good();
 }