diff --git a/packaging/redhat/postgresql10-firebird_fdw.spec b/packaging/redhat/postgresql10-firebird_fdw.spec
index 49f760c..9e22367 100644
--- a/packaging/redhat/postgresql10-firebird_fdw.spec
+++ b/packaging/redhat/postgresql10-firebird_fdw.spec
@@ -26,13 +26,13 @@ This code is very much work-in-progress; USE AT YOUR OWN RISK.
 %setup
 
 %build
-
-PG_CPPFLAGS="-I/usr/include/firebird" make
+export PG_CONFIG=%{pgsql_path}/bin/pg_config
+PG_CPPFLAGS="-I/usr/include/firebird" USE_PGXS=1 make
 
 %install
 rm -rf $RPM_BUILD_ROOT
 export PG_CONFIG=%{pgsql_path}/bin/pg_config
-make DESTDIR=$RPM_BUILD_ROOT install
+USE_PGXS=1 make DESTDIR=$RPM_BUILD_ROOT install
 
 %clean
 rm -rf $RPM_BUILD_ROOT
diff --git a/packaging/redhat/postgresql93-firebird_fdw.spec b/packaging/redhat/postgresql93-firebird_fdw.spec
index 21494e7..e713278 100644
--- a/packaging/redhat/postgresql93-firebird_fdw.spec
+++ b/packaging/redhat/postgresql93-firebird_fdw.spec
@@ -26,13 +26,13 @@ This code is very much work-in-progress; USE AT YOUR OWN RISK.
 %setup
 
 %build
-
-PG_CPPFLAGS="-I/usr/include/firebird" make
+export PG_CONFIG=%{pgsql_path}/bin/pg_config
+PG_CPPFLAGS="-I/usr/include/firebird" USE_PGXS=1 make
 
 %install
 rm -rf $RPM_BUILD_ROOT
 export PG_CONFIG=%{pgsql_path}/bin/pg_config
-make DESTDIR=$RPM_BUILD_ROOT install
+USE_PGXS=1 make DESTDIR=$RPM_BUILD_ROOT install
 
 %clean
 rm -rf $RPM_BUILD_ROOT
diff --git a/packaging/redhat/postgresql94-firebird_fdw.spec b/packaging/redhat/postgresql94-firebird_fdw.spec
index 07c2269..373549a 100644
--- a/packaging/redhat/postgresql94-firebird_fdw.spec
+++ b/packaging/redhat/postgresql94-firebird_fdw.spec
@@ -26,13 +26,13 @@ This code is very much work-in-progress; USE AT YOUR OWN RISK.
 %setup
 
 %build
-
-PG_CPPFLAGS="-I/usr/include/firebird" make
+export PG_CONFIG=%{pgsql_path}/bin/pg_config
+PG_CPPFLAGS="-I/usr/include/firebird" USE_PGXS=1 make
 
 %install
 rm -rf $RPM_BUILD_ROOT
 export PG_CONFIG=%{pgsql_path}/bin/pg_config
-make DESTDIR=$RPM_BUILD_ROOT install
+USE_PGXS=1 make DESTDIR=$RPM_BUILD_ROOT install
 
 %clean
 rm -rf $RPM_BUILD_ROOT
diff --git a/packaging/redhat/postgresql95-firebird_fdw.spec b/packaging/redhat/postgresql95-firebird_fdw.spec
index 070f875..7b51353 100644
--- a/packaging/redhat/postgresql95-firebird_fdw.spec
+++ b/packaging/redhat/postgresql95-firebird_fdw.spec
@@ -26,13 +26,13 @@ This code is very much work-in-progress; USE AT YOUR OWN RISK.
 %setup
 
 %build
-
-PG_CPPFLAGS="-I/usr/include/firebird" make
+export PG_CONFIG=%{pgsql_path}/bin/pg_config
+PG_CPPFLAGS="-I/usr/include/firebird" USE_PGXS=1 make
 
 %install
 rm -rf $RPM_BUILD_ROOT
 export PG_CONFIG=%{pgsql_path}/bin/pg_config
-make DESTDIR=$RPM_BUILD_ROOT install
+USE_PGXS=1 make DESTDIR=$RPM_BUILD_ROOT install
 
 %clean
 rm -rf $RPM_BUILD_ROOT
diff --git a/packaging/redhat/postgresql96-firebird_fdw.spec b/packaging/redhat/postgresql96-firebird_fdw.spec
index 92b63dd..19011bd 100644
--- a/packaging/redhat/postgresql96-firebird_fdw.spec
+++ b/packaging/redhat/postgresql96-firebird_fdw.spec
@@ -26,13 +26,13 @@ This code is very much work-in-progress; USE AT YOUR OWN RISK.
 %setup
 
 %build
-
-PG_CPPFLAGS="-I/usr/include/firebird" make
+export PG_CONFIG=%{pgsql_path}/bin/pg_config
+PG_CPPFLAGS="-I/usr/include/firebird" USE_PGXS=1 make
 
 %install
 rm -rf $RPM_BUILD_ROOT
 export PG_CONFIG=%{pgsql_path}/bin/pg_config
-make DESTDIR=$RPM_BUILD_ROOT install
+USE_PGXS=1 make DESTDIR=$RPM_BUILD_ROOT install
 
 %clean
 rm -rf $RPM_BUILD_ROOT