diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 13b648cab29e..c3314b44a30b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-06-26  Robin Dapp  <rdapp@linux.vnet.ibm.com>
+
+        * config/s390/s390.h (enum processor_flags): Do not use
+        default tune parameter when -march was specified.
+
 2018-06-26  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/86314
diff --git a/gcc/config/s390/s390.h b/gcc/config/s390/s390.h
index de71fd927e21..71a12b8c92ee 100644
--- a/gcc/config/s390/s390.h
+++ b/gcc/config/s390/s390.h
@@ -205,7 +205,7 @@ enum processor_flags
 #define OPTION_DEFAULT_SPECS 					\
   { "mode", "%{!mesa:%{!mzarch:-m%(VALUE)}}" },			\
   { "arch", "%{!march=*:-march=%(VALUE)}" },			\
-  { "tune", "%{!mtune=*:-mtune=%(VALUE)}" }
+  { "tune", "%{!mtune=*:%{!march=*:-mtune=%(VALUE)}}" }
 
 #ifdef __s390__
 extern const char *s390_host_detect_local_cpu (int argc, const char **argv);