diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 75ce12a8c3e..801c806032e 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -133,7 +133,7 @@ static void main_nix_build(int argc, char * * argv)
         script = argv[1];
         try {
             auto lines = tokenizeString<Strings>(readFile(script), "\n");
-            if (std::regex_search(lines.front(), std::regex("^#!"))) {
+            if (!lines.empty() && std::regex_search(lines.front(), std::regex("^#!"))) {
                 lines.pop_front();
                 inShebang = true;
                 for (int i = 2; i < argc; ++i)