diff --git a/postgresql-llvm-optional.patch b/postgresql-llvm-optional.patch
new file mode 100644
index 0000000..87a8d9f
--- /dev/null
+++ b/postgresql-llvm-optional.patch
@@ -0,0 +1,16 @@
+--- src/Makefile.global.in.orig
++++ src/Makefile.global.in
+@@ -192,7 +192,12 @@ with_krb_srvnam	= @with_krb_srvnam@
+ with_ldap	= @with_ldap@
+ with_libxml	= @with_libxml@
+ with_libxslt	= @with_libxslt@
+-with_llvm	= @with_llvm@
++# Only build for LLVM, if the core supports it and the llvm and clang packages are installed.
++ifeq (@with_llvm@ $(wildcard /usr/bin/clang /usr/bin/llvm-lto),yes /usr/bin/clang /usr/bin/llvm-lto)
++with_llvm	= yes
++else
++with_llvm	= no
++endif
+ with_system_tzdata = @with_system_tzdata@
+ with_uuid	= @with_uuid@
+ with_zlib	= @with_zlib@
diff --git a/postgresql12.changes b/postgresql12.changes
index 44d893f..d43b217 100644
--- a/postgresql12.changes
+++ b/postgresql12.changes
@@ -11,6 +11,12 @@ Tue Aug 24 13:01:54 UTC 2021 - Marcus Rueckert <mrueckert@suse.de>
     be crashes or incorrect query results. Disclosure of server
     memory contents is also possible.
 
+-------------------------------------------------------------------
+Fri Jul  2 07:47:15 UTC 2021 - Reinhard Max <max@suse.com>
+
+- bsc#1187751: Make the dependency of postgresqlXX-server-devel on
+  llvm and clang optional (postgresql-llvm-optional.patch).
+
 -------------------------------------------------------------------
 Wed May 19 15:24:24 UTC 2021 - Reinhard Max <max@suse.com>
 
diff --git a/postgresql12.spec b/postgresql12.spec
index bfba53a..5806dda 100644
--- a/postgresql12.spec
+++ b/postgresql12.spec
@@ -88,6 +88,7 @@ BuildRequires:  %libpq
 %bcond_with     systemd
 %bcond_with     systemd_notify
 %endif
+
 %if 0%{?suse_version} >= 1500 && %pgsuffix >= 11 && %pgsuffix < 90
 %bcond_without  llvm
 %else
@@ -153,6 +154,7 @@ Patch4:         postgresql-plperl-keep-rpath.patch
 Patch6:         postgresql-testsuite-int8.sql.patch
 Patch8:         postgresql-testsuite-keep-results-file.patch
 Patch9:         postgresql-var-run-socket.patch
+Patch10:        postgresql-llvm-optional.patch
 URL:            https://www.postgresql.org/
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 Provides:       postgresql = %version-%release
@@ -255,8 +257,8 @@ Requires:       %pgname-server = %version-%release
 Provides:       postgresql-server-devel-exclusive = %pgmajor
 Conflicts:      postgresql-server-devel-exclusive < %pgmajor
 %if %{with llvm}
-Requires:       clang
-Requires:       llvm
+Recommends:     clang
+Recommends:     llvm
 %endif
 Requires:       libxslt-devel
 Requires:       openssl-devel
@@ -459,6 +461,7 @@ touch -r configure tmp
 %patch6
 %patch8 -p1
 %patch9
+%patch10
 touch -r tmp configure
 rm tmp
 find src/test/ -name '*.orig' -delete
@@ -533,8 +536,7 @@ make check || {
 %endif
 
 %install
-VLANG=${RPM_PACKAGE_VERSION%%.*}
-VSO=${RPM_PACKAGE_VERSION%%%%.*}
+VLANG=%pgmajor
 %if %mini
 make DESTDIR=%buildroot PACKAGE_TARNAME=%pgname -C src/include install
 make DESTDIR=%buildroot PACKAGE_TARNAME=%pgname -C src/interfaces install