diff --git a/var/spack/repos/builtin/packages/opencv/package.py b/var/spack/repos/builtin/packages/opencv/package.py
index 6ff132fc6f4..a49b8931fba 100644
--- a/var/spack/repos/builtin/packages/opencv/package.py
+++ b/var/spack/repos/builtin/packages/opencv/package.py
@@ -929,9 +929,11 @@ def cmake_args(self):
         ]
 
         if self.spec.satisfies("+contrib"):
-            args += self.define(
-                "OPENCV_EXTRA_MODULES_PATH",
-                join_path(self.stage.source_path, "opencv_contrib", "modules"),
+            args.append(
+                self.define(
+                    "OPENCV_EXTRA_MODULES_PATH",
+                    join_path(self.stage.source_path, "opencv_contrib", "modules"),
+                )
             )
 
         # OpenCV pre-built apps