diff --git a/dlls/mshtml/htmlwindow.c b/dlls/mshtml/htmlwindow.c
index 9da2f7ccbae..e535cd54bd6 100644
--- a/dlls/mshtml/htmlwindow.c
+++ b/dlls/mshtml/htmlwindow.c
@@ -1734,7 +1734,7 @@ static HRESULT WINAPI HTMLWindow3_detachEvent(IHTMLWindow3 *iface, BSTR event, I
 }
 
 static HRESULT window_set_timer(HTMLInnerWindow *This, VARIANT *expr, LONG msec, VARIANT *language,
-        BOOL interval, LONG *timer_id)
+        enum timer_type timer_type, LONG *timer_id)
 {
     IDispatch *disp = NULL;
     HRESULT hres;
@@ -1757,7 +1757,7 @@ static HRESULT window_set_timer(HTMLInnerWindow *This, VARIANT *expr, LONG msec,
     if(!disp)
         return E_FAIL;
 
-    hres = set_task_timer(This, msec, interval, disp, timer_id);
+    hres = set_task_timer(This, msec, timer_type, disp, timer_id);
     IDispatch_Release(disp);
 
     return hres;
@@ -1770,7 +1770,7 @@ static HRESULT WINAPI HTMLWindow3_setTimeout(IHTMLWindow3 *iface, VARIANT *expre
 
     TRACE("(%p)->(%s %d %s %p)\n", This, debugstr_variant(expression), msec, debugstr_variant(language), timerID);
 
-    return window_set_timer(This->inner_window, expression, msec, language, FALSE, timerID);
+    return window_set_timer(This->inner_window, expression, msec, language, TIMER_TIMEOUT, timerID);
 }
 
 static HRESULT WINAPI HTMLWindow3_setInterval(IHTMLWindow3 *iface, VARIANT *expression, LONG msec,
@@ -1780,7 +1780,7 @@ static HRESULT WINAPI HTMLWindow3_setInterval(IHTMLWindow3 *iface, VARIANT *expr
 
     TRACE("(%p)->(%p %d %p %p)\n", This, expression, msec, language, timerID);
 
-    return window_set_timer(This->inner_window, expression, msec, language, TRUE, timerID);
+    return window_set_timer(This->inner_window, expression, msec, language, TIMER_INTERVAL, timerID);
 }
 
 static HRESULT WINAPI HTMLWindow3_print(IHTMLWindow3 *iface)
diff --git a/dlls/mshtml/mshtml_private.h b/dlls/mshtml/mshtml_private.h
index adb71014acb..4cbddb68022 100644
--- a/dlls/mshtml/mshtml_private.h
+++ b/dlls/mshtml/mshtml_private.h
@@ -1213,7 +1213,12 @@ LONG get_task_target_magic(void) DECLSPEC_HIDDEN;
 HRESULT push_task(task_t*,task_proc_t,task_proc_t,LONG) DECLSPEC_HIDDEN;
 void remove_target_tasks(LONG) DECLSPEC_HIDDEN;
 
-HRESULT set_task_timer(HTMLInnerWindow*,LONG,BOOL,IDispatch*,LONG*) DECLSPEC_HIDDEN;
+enum timer_type {
+    TIMER_TIMEOUT,
+    TIMER_INTERVAL,
+};
+
+HRESULT set_task_timer(HTMLInnerWindow*,LONG,enum timer_type,IDispatch*,LONG*) DECLSPEC_HIDDEN;
 HRESULT clear_task_timer(HTMLInnerWindow*,DWORD) DECLSPEC_HIDDEN;
 
 BOOL parse_compat_version(const WCHAR*,compat_mode_t*) DECLSPEC_HIDDEN;
diff --git a/dlls/mshtml/task.c b/dlls/mshtml/task.c
index f9d06407fb3..c26f3754fd4 100644
--- a/dlls/mshtml/task.c
+++ b/dlls/mshtml/task.c
@@ -41,6 +41,7 @@ typedef struct {
     DWORD id;
     DWORD time;
     DWORD interval;
+    enum timer_type type;
     IDispatch *disp;
 
     struct list entry;
@@ -162,7 +163,7 @@ static BOOL queue_timer(thread_data_t *thread_data, task_timer_t *timer)
     return FALSE;
 }
 
-HRESULT set_task_timer(HTMLInnerWindow *window, LONG msec, BOOL interval, IDispatch *disp, LONG *id)
+HRESULT set_task_timer(HTMLInnerWindow *window, LONG msec, enum timer_type timer_type, IDispatch *disp, LONG *id)
 {
     thread_data_t *thread_data;
     task_timer_t *timer;
@@ -184,7 +185,8 @@ HRESULT set_task_timer(HTMLInnerWindow *window, LONG msec, BOOL interval, IDispa
     timer->id = id_cnt++;
     timer->window = window;
     timer->time = tc + msec;
-    timer->interval = interval ? msec : 0;
+    timer->interval = timer_type == TIMER_INTERVAL ? msec : 0;
+    timer->type = timer_type;
     list_init(&timer->entry);
 
     IDispatch_AddRef(disp);