diff --git a/var/spack/repos/builtin/packages/lhapdf/package.py b/var/spack/repos/builtin/packages/lhapdf/package.py
index b02efbd3422..a58107b8a20 100644
--- a/var/spack/repos/builtin/packages/lhapdf/package.py
+++ b/var/spack/repos/builtin/packages/lhapdf/package.py
@@ -45,7 +45,7 @@ def configure_args(self):
         args = ["FCFLAGS=-O3", "CFLAGS=-O3", "CXXFLAGS=-O3"]
 
         if self.spec.satisfies("+python"):
-            args.extend(
+            args.append(
                 "LIBS=-L"
                 + self.spec["python"].prefix.lib
                 + " -L"