diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index d80dd46c5fdb..e3c4a0525ad7 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -444,6 +444,59 @@ make check LANG=C ENCODING=EUC_JP
+
+ Path Substitution
+
+
+ The test suites driven by pg_regress can use the
+ following environment variables for path substitutions:
+
+
+
+ PG_ABS_SRCDIR
+
+
+ Absolute path to the source directory.
+
+
+
+
+
+ PG_ABS_BUILDDIR
+
+
+ Absolute path to the build directory.
+
+
+
+
+
+ PG_DLSUFFIX
+
+
+ Name of extension for dynamically-loadable modules (e.g.
+ .so on Linux).
+
+
+
+
+
+ PG_LIBDIR
+
+
+ Absolute path to dynamic libraries.
+
+
+
+
+
+ These are useful when dealing with function and object loading
+ that require specific paths to work, like paths defined in a
+ CREATE FUNCTION or LOAD
+ command, for example.
+
+
+
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