diff --git a/api/boinc_api.C b/api/boinc_api.C
index 023060a836..787f12fbfa 100644
--- a/api/boinc_api.C
+++ b/api/boinc_api.C
@@ -619,6 +619,7 @@ static void worker_timer(int /*a*/) {
 
 #ifndef _WIN32
 void* timer_thread(void*) {
+    block_sigalrm();
     while(1) {
         boinc_sleep(TIMER_PERIOD);
         worker_timer(0);
@@ -789,4 +790,15 @@ void boinc_fpops_cumulative(double x) {
     fpops_cumulative = x;
 }
 
+#ifndef _WIN32
+// block SIGALRM, so that the worker thread will be forced to handle it
+//
+void block_sigalrm() {
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGALRM);
+    pthread_sigmask(SIG_BLOCK, &mask, NULL);
+}
+#endif
+
 const char *BOINC_RCSID_0fa0410386 = "$Id$";
diff --git a/api/boinc_api.h b/api/boinc_api.h
index d3307ac352..3b90e48e13 100755
--- a/api/boinc_api.h
+++ b/api/boinc_api.h
@@ -118,6 +118,8 @@ extern void options_defaults(BOINC_OPTIONS&);
 extern APP_CLIENT_SHM *app_client_shm;
 #ifdef _WIN32
 extern HANDLE worker_thread_handle;
+#else
+extern void block_sigalrm();
 #endif
 extern int boinc_init_options_general(BOINC_OPTIONS& opt);
 extern int set_worker_timer(void);
diff --git a/api/graphics_impl.C b/api/graphics_impl.C
index 182379c1e8..50b1ec8bd2 100755
--- a/api/graphics_impl.C
+++ b/api/graphics_impl.C
@@ -141,12 +141,7 @@ int start_worker_thread(WORKER_FUNC_PTR _worker_main) {
     if (retval) return ERR_THREAD;
     pthread_attr_destroy( &worker_thread_attr );
 
-    // block SIGLARM, so that the worker thread will be forced to handle it
-    //
-    sigset_t mask;
-    sigemptyset(&mask);
-    sigaddset(&mask, SIGALRM);
-    pthread_sigmask(SIG_BLOCK, &mask, NULL);
+    block_sigalrm();
 #endif
     return 0;
 }
diff --git a/checkin_notes b/checkin_notes
index a6d93aa12d..1ef4f91ee8 100755
--- a/checkin_notes
+++ b/checkin_notes
@@ -10403,3 +10403,12 @@ Rom    11 Aug 2005
         ValidateAccountKey.cpp
         ValidateURL.cpp
         WizAttachProject.cpp, .h
+
+David  11 Aug 2005
+    - API bug fix: block SIGALRM in timer thread
+        (make new function block_sigalrm();
+        call it from graphics, timer thread)
+
+    api/
+        boinc_api.C,h
+        graphics_impl.C