diff --git a/MozillaThunderbird.changes b/MozillaThunderbird.changes
index 2d2916a..4dc7f6c 100644
--- a/MozillaThunderbird.changes
+++ b/MozillaThunderbird.changes
@@ -1,3 +1,9 @@
+-------------------------------------------------------------------
+Thu Jun  1 06:09:23 UTC 2017 - wr@rosenauer.org
+
+- explicitely optimize with -O2 for openSUSE > 13.2/Leap 42 to work
+  with gcc7 (boo#1040105, boo#1042090)
+
 -------------------------------------------------------------------
 Thu May 11 21:16:41 UTC 2017 - wr@rosenauer.org
 
diff --git a/MozillaThunderbird.spec b/MozillaThunderbird.spec
index 253ec31..83b5381 100644
--- a/MozillaThunderbird.spec
+++ b/MozillaThunderbird.spec
@@ -260,7 +260,15 @@ ac_add_options --includedir=%{_includedir}
 ac_add_options --disable-tests
 ac_add_options --disable-debug
 ac_add_options --enable-alsa
-ac_add_options --enable-optimize
+# gcc7 (boo#104105)
+%if 0%{?suse_version} > 1320
+ac_add_options --enable-optimize="-g -O2"
+%endif
+farch %ix86 %arm
+%if 0%{?suse_version} > 1230
+ac_add_options --disable-optimize
+%endif
+%endif
 %if 0%{?mozilla_use_gtk3}
 ac_add_options --enable-default-toolkit=cairo-gtk3
 %else