diff --git a/src/engine/mailprivacy_smime.c b/src/engine/mailprivacy_smime.c
index 42feeac..4ebd9d2 100644
--- a/src/engine/mailprivacy_smime.c
+++ b/src/engine/mailprivacy_smime.c
@@ -39,6 +39,11 @@
 
 #include "mailprivacy_smime.h"
 #include <string.h>
+
+#if __APPLE__
+#include <TargetConditionals.h>
+#endif
+
 #ifdef WIN32
 #	include "win_etpan.h"
 #	define WEXITSTATUS(r) (r)
@@ -1542,6 +1547,12 @@ static int get_cert_from_sig(struct mailprivacy * privacy,
   int r;
   char command[PATH_MAX];
 
+#if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR
+  //https://github.com/dinhviethoa/libetpan/issues/275
+  //get_cert_from_sig is not needed on iOS
+  return MAIL_ERROR_COMMAND;
+#endif
+
   if (* cert_dir == '\0')
     return MAIL_ERROR_INVAL;
 
@@ -1561,7 +1572,7 @@ static int get_cert_from_sig(struct mailprivacy * privacy,
   cur = clist_begin(mime->mm_data.mm_multipart.mm_mp_list);
   if (cur == NULL) {
     res = MAIL_ERROR_INVAL;
-    goto err;
+   goto err;
   }
   
   signed_mime = cur->data;
@@ -1602,7 +1613,13 @@ static int get_cert_from_sig(struct mailprivacy * privacy,
       "openssl pkcs7 -inform DER -in '%s' -out '%s' -print_certs 2>/dev/null",
       quoted_signature_filename, quoted_store_cert_filename);
   
-  r = system(command);
+// N.B. This is only about compilation - we already don't execute this function with iPhone.
+#if !TARGET_OS_IPHONE && !TARGET_IPHONE_SIMULATOR
+  //https://github.com/dinhviethoa/libetpan/issues/275
+  //system() is not supported on iOS 11.
+   r = system(command);
+#endif
+
   if (WEXITSTATUS(r) != 0) {
     res = MAIL_ERROR_COMMAND;
     goto unlink_signature;
diff --git a/src/engine/mailprivacy_tools.c b/src/engine/mailprivacy_tools.c
index 81d279c..e835247 100644
--- a/src/engine/mailprivacy_tools.c
+++ b/src/engine/mailprivacy_tools.c
@@ -40,6 +40,10 @@
 #include "mailprivacy_tools.h"
 #include "mailprivacy_tools_private.h"
 
+#if __APPLE__
+#include <TargetConditionals.h>
+#endif
+
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -1331,6 +1335,12 @@ int mailprivacy_spawn_and_wait(char * command, char * passphrase,
     char * stdoutfile, char * stderrfile,
     int * bad_passphrase)
 {
+#if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR
+  //https://github.com/dinhviethoa/libetpan/issues/275
+  //mailprivacy_spawn_and_wait is not needed on iOS
+  return MAIL_ERROR_COMMAND;
+#endif
+
 #ifdef WIN32
   int res;
   SECURITY_ATTRIBUTES sec_attr;
@@ -1517,11 +1527,16 @@ int mailprivacy_spawn_and_wait(char * command, char * passphrase,
       Dup2(fd_err, 2);
       Close(fd_err);
  
+#if !TARGET_OS_IPHONE && !TARGET_IPHONE_SIMULATOR
+      //https://github.com/dinhviethoa/libetpan/issues/275
+      //system() is not supported on iOS 11.
+
       // BUG: status may be -1 and errno may be EINTR if waitpid(2) was
       // interrupted by a signal; to handle that properly the PID of the
       // fork(2)ed child has to be determined and waitpid(2) has to be
       // called again
       status = system(command);
+#endif
       
       exit(WEXITSTATUS(status));
     }