diff --git a/src/ioslaves/trash/tests/CMakeLists.txt b/src/ioslaves/trash/tests/CMakeLists.txt
index 514fd79c..99897530 100644
--- a/src/ioslaves/trash/tests/CMakeLists.txt
+++ b/src/ioslaves/trash/tests/CMakeLists.txt
@@ -1,30 +1,33 @@
 include_directories( ${CMAKE_CURRENT_SOURCE_DIR}/.. )
 
 ########### next target ###############
 
-set(testtrash_SRCS 
-    testtrash.cpp 
+set(testtrash_SRCS
+    testtrash.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/../trashimpl.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/../trashsizecache.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/../discspaceutil.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/../kinterprocesslock.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/../kiotrashdebug.cpp
 )
 
 if(APPLE)
     set(testtrash_APPLE_LIBS "-framework DiskArbitration -framework CoreFoundation")
 endif(APPLE)
 
 include(ECMAddTests)
 
 ecm_add_test(${testtrash_SRCS}
     TEST_NAME testtrash
     LINK_LIBRARIES KF5::I18n Qt5::DBus KF5::KIOCore KF5::Solid Qt5::Test ${testtrash_APPLE_LIBS}
 )
 
+# other tests like dropjob and fileundomanager use the trash in ~/.qttest, which this test cleans up
+set_tests_properties(testtrash PROPERTIES RUN_SERIAL TRUE)
+
 ### next target ###
 
 add_executable(lockingtest lockingtest.cpp ../kinterprocesslock.cpp)
 ecm_mark_nongui_executable(lockingtest)
 
 target_link_libraries(lockingtest Qt5::Core Qt5::DBus)