diff --git a/documentation/RELEASE_NOTES.html b/documentation/RELEASE_NOTES.html
index 9bd61ed34..bb7dd93da 100644
--- a/documentation/RELEASE_NOTES.html
+++ b/documentation/RELEASE_NOTES.html
@@ -16,6 +16,13 @@ Base-3.15 series or to EPICS 7.</p>
 
 <!-- Insert new items immediately below here ... -->
 
+<h3>Recent Apple XCode Build Issues</h3>
+
+<p>The latest version of XCode will not compile calls to <tt>system()</tt> or
+<tt>clock_settime()</tt> for iOS targets. There were several places in Base
+where these were being compiled, although there were probably never called. The
+code has now been modified to permit iOS builds to complete again.</p>
+
 <h3>Prevent illegal alarm severities</h3>
 
 <p>A check has been added to <tt>recGblResetAlarms()</tt> that prevents records
diff --git a/src/misc/Makefile b/src/misc/Makefile
index 3d7bc5168..a35391aeb 100644
--- a/src/misc/Makefile
+++ b/src/misc/Makefile
@@ -26,6 +26,7 @@ LIB_SRCS += miscIocRegister.c
 LIB_SRCS += dlload.c
 LIB_SRCS += iocshRegisterCommon.c
 
+miscIocRegister_CFLAGS_iOS = -DSYSTEM_UNAVAILABLE
 
 LIBRARY_IOC = miscIoc
 
diff --git a/src/misc/miscIocRegister.c b/src/misc/miscIocRegister.c
index 0d482f7cf..d892f637a 100644
--- a/src/misc/miscIocRegister.c
+++ b/src/misc/miscIocRegister.c
@@ -66,10 +66,12 @@ void epicsShareAPI miscIocRegister(void)
 
 /* system -- escape to system command interpreter.
  *
- * Disabled by default, for security reasons. To enable this command, add
+ * Disabled by default for security reasons, not available on all OSs.
+ * To enable this command, add
  *     registrar(iocshSystemCommand)
- * to an application dbd file.
+ * to an application dbd file, or include system.dbd
  */
+#ifndef SYSTEM_UNAVAILABLE
 static const iocshArg systemArg0 = { "command string",iocshArgString};
 static const iocshArg * const systemArgs[] = {&systemArg0};
 static const iocshFuncDef systemFuncDef = {"system",1,systemArgs};
@@ -77,12 +79,15 @@ static void systemCallFunc(const iocshArgBuf *args)
 {
     system(args[0].sval);
 }
+#endif
 
 static void iocshSystemCommand(void)
 {
+#ifndef SYSTEM_UNAVAILABLE
     if (system(NULL))
         iocshRegister(&systemFuncDef, systemCallFunc);
     else
+#endif
         errlogPrintf ("Can't register 'system' command -- no command interpreter available.\n");
 }
 epicsExportRegistrar(iocshSystemCommand);