diff --git a/brp-mangle-shebangs b/brp-mangle-shebangs
index 4fa8daa..67a1a7d 100755
--- a/brp-mangle-shebangs
+++ b/brp-mangle-shebangs
@@ -129,8 +129,8 @@ while IFS= read -r -d $'\0' f; do
   py_shebang=$(echo "$shebang" | sed -r -e 's@/usr/bin/python(\s|$)@/usr/bin/python2\1@')
 
   if [ "$shebang" != "$py_shebang" ]; then
-    sed -i -e "1c #!$py_shebang" "$f"
-    echo >&2 "*** WARNING: mangling shebang in $path from #!$orig_shebang to #!$py_shebang. This will become an ERROR, fix it manually!"
+    echo >&2 "*** ERROR: ambiguous python shebang in $path: #!$orig_shebang. Change it to python3 (or python2) explicitly."
+    fail=1
   elif [ "#!$shebang" != "#!$orig_shebang" ]; then
     sed -i -e "1c #!$shebang" "$f"
     echo "mangling shebang in $path from $orig_shebang to #!$shebang"
diff --git a/redhat-rpm-config.spec b/redhat-rpm-config.spec
index b7c0c77..a2c9132 100644
--- a/redhat-rpm-config.spec
+++ b/redhat-rpm-config.spec
@@ -6,7 +6,7 @@
 
 Summary: Red Hat specific rpm configuration files
 Name: redhat-rpm-config
-Version: 119
+Version: 120
 Release: 1%{?dist}
 # No version specified.
 License: GPL+
@@ -183,6 +183,10 @@ install -p -m 755 -t %{buildroot}%{_rpmconfigdir} kmod.prov
 %{_rpmconfigdir}/macros.d/macros.kmp
 
 %changelog
+* Mon Sep 10 2018 Miro Hrončok <mhroncok@redhat.com> - 120-1
+- Make ambiguous python shebangs error
+  https://fedoraproject.org/wiki/Changes/Make_ambiguous_python_shebangs_error
+
 * Mon Aug 20 2018 Kalev Lember <klember@redhat.com> - 119-1
 - Add aarch64 to ldc arches