diff --git a/clientscr/Mac_Saver_Module.h b/clientscr/Mac_Saver_Module.h
index 86e12067b1..49e2f4fdd6 100644
--- a/clientscr/Mac_Saver_Module.h
+++ b/clientscr/Mac_Saver_Module.h
@@ -48,6 +48,7 @@ void            setGFXDefaultPeriod(double value);
 void            setGFXSciencePeriod(double value);
 void            setGGFXChangePeriod(double value);
 double          getDTime();
+void            doBoinc_Sleep(double seconds);
 void            print_to_log_file(const char *format, ...);
 void            strip_cr(char *buf);
 void            PrintBacktrace(void);
diff --git a/clientscr/Mac_Saver_ModuleView.h b/clientscr/Mac_Saver_ModuleView.h
index e3cf558eb2..3adfeced3a 100644
--- a/clientscr/Mac_Saver_ModuleView.h
+++ b/clientscr/Mac_Saver_ModuleView.h
@@ -57,4 +57,5 @@ void            setGFXSciencePeriod(double value);
 void            setGGFXChangePeriod(double value);
 bool            validateNumericString(CFStringRef s);
 double          getDTime();
+void            doBoinc_Sleep(double seconds);
 extern void     print_to_log_file(const char *format, ...);
diff --git a/clientscr/Mac_Saver_ModuleView.m b/clientscr/Mac_Saver_ModuleView.m
index 8ab4fb2941..9f1afac10e 100644
--- a/clientscr/Mac_Saver_ModuleView.m
+++ b/clientscr/Mac_Saver_ModuleView.m
@@ -244,7 +244,7 @@ int signof(float x) {
     NSPoint imagePosition;
     char *msg;
     CFStringRef cf_msg;
-    AbsoluteTime timeToUnblock, frameStartTime = UpTime();
+    double timeToBlock, frameStartTime = getDTime();
     kern_return_t   kernResult = kIOReturnError; 
     UInt64          params;
     IOByteCount     rcnt = sizeof(UInt64);
@@ -490,8 +490,10 @@ int signof(float x) {
         [ self setAnimationTimeInterval:(1.0/newFrequency) ];
         // setAnimationTimeInterval does not seem to be working, so we 
         // throttle the screensaver directly here.
-        timeToUnblock = AddDurationToAbsolute(durationSecond/newFrequency, frameStartTime);
-        MPDelayUntil(&timeToUnblock);
+        timeToBlock = (1.0/newFrequency) - (getDTime() - frameStartTime);
+        if (timeToBlock > 0.0) {
+            doBoinc_Sleep(timeToBlock);
+        }
     }
 }
 
diff --git a/clientscr/mac_saver_module.cpp b/clientscr/mac_saver_module.cpp
index 3efef198d5..b3f43aa982 100644
--- a/clientscr/mac_saver_module.cpp
+++ b/clientscr/mac_saver_module.cpp
@@ -222,6 +222,11 @@ double getDTime() {
 }
 
 
+void doBoinc_Sleep(double seconds) {
+    boinc_sleep(seconds);
+}
+
+
 CScreensaver::CScreensaver() {
     struct ss_periods periods;