diff --git a/tests/docker/Makefile.include b/tests/docker/Makefile.include
index 2fd2ca305716..134dc6fff406 100644
--- a/tests/docker/Makefile.include
+++ b/tests/docker/Makefile.include
@@ -28,8 +28,7 @@ make-archive-maybe = $(if $(wildcard $1/*), \
 		"  ARCHIVE $(notdir $2)"))
 
 CUR_TIME := $(shell date +%Y-%m-%d-%H.%M.%S.$$$$)
-# Makes the definition constant after the first expansion
-DOCKER_SRC_COPY = $(eval DOCKER_SRC_COPY := docker-src.$(CUR_TIME))$(DOCKER_SRC_COPY)
+DOCKER_SRC_COPY := docker-src.$(CUR_TIME)
 
 $(DOCKER_SRC_COPY):
 	@mkdir $@