diff --git a/doc/src/sgml/extend.sgml b/doc/src/sgml/extend.sgml
index 695e07fb38..421e059e7b 100644
--- a/doc/src/sgml/extend.sgml
+++ b/doc/src/sgml/extend.sgml
@@ -1325,7 +1325,34 @@ include $(PGXS)
       <term><varname>PG_CPPFLAGS</varname></term>
       <listitem>
        <para>
-        will be added to <varname>CPPFLAGS</varname>
+        will be prepended to <varname>CPPFLAGS</varname>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><varname>PG_CFLAGS</varname></term>
+      <listitem>
+       <para>
+        will be appended to <varname>CFLAGS</varname>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><varname>PG_CXXFLAGS</varname></term>
+      <listitem>
+       <para>
+        will be appended to <varname>CXXFLAGS</varname>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><varname>PG_LDFLAGS</varname></term>
+      <listitem>
+       <para>
+        will be prepended to <varname>LDFLAGS</varname>
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/makefiles/pgxs.mk b/src/makefiles/pgxs.mk
index 74942b6e19..123bdffaa6 100644
--- a/src/makefiles/pgxs.mk
+++ b/src/makefiles/pgxs.mk
@@ -49,7 +49,10 @@
 #   NO_INSTALLCHECK -- don't define an installcheck target, useful e.g. if
 #     tests require special configuration, or don't use pg_regress
 #   EXTRA_CLEAN -- extra files to remove in 'make clean'
-#   PG_CPPFLAGS -- will be added to CPPFLAGS
+#   PG_CPPFLAGS -- will be prepended to CPPFLAGS
+#   PG_CFLAGS -- will be appended to CFLAGS
+#   PG_CXXFLAGS -- will be appended to CXXFLAGS
+#   PG_LDFLAGS -- will be prepended to LDFLAGS
 #   PG_LIBS -- will be added to PROGRAM link line
 #   PG_LIBS_INTERNAL -- same, for references to libraries within build tree
 #   SHLIB_LINK -- will be added to MODULE_big link line
@@ -116,6 +119,15 @@ endif
 ifdef PG_CPPFLAGS
 override CPPFLAGS := $(PG_CPPFLAGS) $(CPPFLAGS)
 endif
+ifdef PG_CFLAGS
+override CFLAGS := $(CFLAGS) $(PG_CFLAGS)
+endif
+ifdef PG_CXXFLAGS
+override CXXFLAGS := $(CXXFLAGS) $(PG_CXXFLAGS)
+endif
+ifdef PG_LDFLAGS
+override LDFLAGS := $(PG_LDFLAGS) $(LDFLAGS)
+endif
 
 # logic for HEADERS_* stuff