diff --git a/tests/test-selection-getter.lua b/tests/test-selection-getter.lua
index 9d919355..afac4703 100644
--- a/tests/test-selection-getter.lua
+++ b/tests/test-selection-getter.lua
@@ -8,6 +8,8 @@ local lgi = require("lgi")
 local Gio = lgi.Gio
 local GdkPixbuf = lgi.GdkPixbuf
 
+local pids = {}
+
 local lua_executable = os.getenv("LUA")
 if lua_executable == nil or lua_executable == "" then
     lua_executable = "lua"
@@ -53,8 +55,9 @@ runner.run_steps{
 
     -- Clear the clipboard to get to a known state
     function()
-        spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
             { exit = function() continue = true end })
+        table.insert(pids, pid)
         return true
     end,
 
@@ -84,13 +87,15 @@ runner.run_steps{
 
         -- Now set the clipboard to some text
         continue = false
-        spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard_text },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard_text },
             { stdout = function(line)
                 assert(line == "initialisation done",
                     "Unexpected line: " .. line)
                 continue = true
             end })
 
+        table.insert(pids, pid)
+
         return true
     end,
 
@@ -148,13 +153,15 @@ runner.run_steps{
 
         -- Now set the clipboard to an image
         continue = false
-        spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard_pixbuf },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard_pixbuf },
             { stdout = function(line)
                 assert(line == "initialisation done",
                     "Unexpected line: " .. line)
                 continue = true
             end })
 
+        table.insert(pids, pid)
+
         return true
     end,
 
@@ -194,6 +201,12 @@ runner.run_steps{
             return
         end
 
+        -- There are now "windows", so they have no "clients", however,
+        -- they talk to X11 and wont exit by themselves and must be killed.
+        for _, pid in ipairs(pids) do
+            awesome.kill(pid, 9)
+        end
+
         return true
     end,
 }
diff --git a/tests/test-selection-watcher.lua b/tests/test-selection-watcher.lua
index 3721a67f..2e9d6a64 100644
--- a/tests/test-selection-watcher.lua
+++ b/tests/test-selection-watcher.lua
@@ -3,6 +3,8 @@
 local runner = require("_runner")
 local spawn = require("awful.spawn")
 
+local pids = {}
+
 local lua_executable = os.getenv("LUA")
 if lua_executable == nil or lua_executable == "" then
     lua_executable = "lua"
@@ -67,8 +69,11 @@ runner.run_steps{
     -- Clear the clipboard to get to a known state
     function()
         check_state(0, 0)
-        spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
             { exit = function() continue = true end })
+
+        table.insert(pids, pid)
+
         return true
     end,
 
@@ -86,13 +91,15 @@ runner.run_steps{
 
         -- Set the clipboard
         continue = false
-        spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_clipboard },
             { stdout = function(line)
                 assert(line == "initialisation done",
                     "Unexpected line: " .. line)
                 continue = true
             end })
 
+        table.insert(pids, pid)
+
         return true
     end,
 
@@ -105,9 +112,11 @@ runner.run_steps{
 
         -- Now clear the clipboard again
         continue = false
-        spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
+        local pid = spawn.with_line_callback({ lua_executable, "-e", acquire_and_clear_clipboard },
             { exit = function() continue = true end })
 
+        table.insert(pids, pid)
+
         return true
     end,
 
@@ -118,6 +127,13 @@ runner.run_steps{
         end
 
         check_state(2, 1)
+
+        -- There are now "windows", so they have no "clients", however,
+        -- they talk to X11 and wont exit by themselves and must be killed.
+        for _, pid in ipairs(pids) do
+            awesome.kill(pid, 9)
+        end
+
         return true
     end
 }