diff --git a/src/pg/Makefile b/src/pg/Makefile
index 4ff713d..ded7121 100644
--- a/src/pg/Makefile
+++ b/src/pg/Makefile
@@ -5,6 +5,8 @@
 #                      and make it available to PostgreSQL
 # PGUSER=postgres make installcheck -- test the 'dev' extension
 
+SED = sed
+
 EXTENSION    = crankshaft
 
 DATA         = $(EXTENSION)--dev.sql \
@@ -14,8 +16,14 @@ DATA         = $(EXTENSION)--dev.sql \
 SOURCES_DATA_DIR = sql
 SOURCES_DATA = $(wildcard $(SOURCES_DATA_DIR)/*.sql)
 
+VIRTUALENV_PATH = $(realpath ../py/)
+ESC_VIRVIRTUALENV_PATH = $(subst /,\/,$(VIRTUALENV_PATH))
+
+REPLACEMENTS = -e 's/@@VERSION@@/$(EXTVERSION)/g' \
+               -e 's/@@VIRTUALENV_PATH@@/$(ESC_VIRVIRTUALENV_PATH)/g'
+
 $(DATA): $(SOURCES_DATA)
-	cat $(SOURCES_DATA_DIR)/*.sql > $@
+	$(SED) $(REPLACEMENTS) $(SOURCES_DATA_DIR)/*.sql > $@
 
 TEST_DIR = test
 REGRESS = $(notdir $(basename $(wildcard $(TEST_DIR)/sql/*test.sql)))
@@ -28,6 +36,7 @@ include $(PGXS)
 # This seems to be needed at least for PG 9.3.11
 all: $(DATA)
 
+
 # WIP: goals for releasing the extension...
 
 EXTVERSION   = $(shell grep default_version $(EXTENSION).control | sed -e "s/default_version[[:space:]]*=[[:space:]]*'\([^']*\)'/\1/")
diff --git a/src/pg/sql/01_py.sql b/src/pg/sql/01_py.sql
deleted file mode 100644
index f1eaa31..0000000
--- a/src/pg/sql/01_py.sql
+++ /dev/null
@@ -1,18 +0,0 @@
--- Use the crankshaft python module
-CREATE OR REPLACE FUNCTION _cdb_crankshaft_activate_py()
-RETURNS VOID
-AS $$
-    # activate virtualenv
-    # TODO: parameterize with environment variables or something
-    venv_path = '/home/ubuntu/crankshaft/src/py/dev'
-    activate_path = venv_path + '/bin/activate_this.py'
-    exec(open(activate_path).read(),
-         dict(__file__=activate_path))
-
-    # import something from virtualenv
-    # from crankshaft import random_seeds
-
-    # do some stuff
-    # random_seeds.set_random_seeds(123)
-    # plpy.notice('here we are')
-$$ LANGUAGE plpythonu;
diff --git a/src/pg/sql/01_version.sql b/src/pg/sql/01_version.sql
new file mode 100644
index 0000000..90e6123
--- /dev/null
+++ b/src/pg/sql/01_version.sql
@@ -0,0 +1,12 @@
+-- Version number of the extension release
+CREATE OR REPLACE FUNCTION cdb_crankshaft_version()
+RETURNS text AS $$
+  SELECT '@@VERSION@@'::text;
+$$ language 'sql' IMMUTABLE STRICT;
+
+-- Internal identifier of the installed extension instence
+-- e.g. 'dev' for current development version
+CREATE OR REPLACE FUNCTION cdb_crankshaft_internal_version()
+RETURNS text AS $$
+  SELECT installed_version FROM pg_available_extensions where name='crankshaft' and pg_available_extensions IS NOT NULL;
+$$ language 'sql' IMMUTABLE STRICT;
diff --git a/src/pg/sql/02_py.sql b/src/pg/sql/02_py.sql
new file mode 100644
index 0000000..a233a0a
--- /dev/null
+++ b/src/pg/sql/02_py.sql
@@ -0,0 +1,23 @@
+CREATE OR REPLACE FUNCTION _cdb_crankshaft_virtualenvs_path()
+RETURNS text
+AS $$
+  BEGIN
+    -- RETURN '/opt/virtualenvs/crankshaft';
+    RETURN '@@VIRTUALENV_PATH@@';
+  END;
+$$ language plpgsql IMMUTABLE STRICT;
+
+-- Use the crankshaft python module
+CREATE OR REPLACE FUNCTION _cdb_crankshaft_activate_py()
+RETURNS VOID
+AS $$
+    import os
+    # plpy.notice('%',str(os.environ))
+    # activate virtualenv
+    crankshaft_version = plpy.execute('SELECT cdb_crankshaft.cdb_crankshaft_internal_version()')[0]['cdb_crankshaft_internal_version']
+    base_path = plpy.execute('SELECT cdb_crankshaft._cdb_crankshaft_virtualenvs_path()')[0]['_cdb_crankshaft_virtualenvs_path']
+    default_venv_path = os.path.join(base_path, crankshaft_version)
+    venv_path =  os.environ.get('CRANKSHAFT_VENV', default_venv_path)
+    activate_path = venv_path + '/bin/activate_this.py'
+    exec(open(activate_path).read(), dict(__file__=activate_path))
+$$ LANGUAGE plpythonu;
diff --git a/src/pg/sql/02_random_seeds.sql b/src/pg/sql/03_random_seeds.sql
similarity index 100%
rename from src/pg/sql/02_random_seeds.sql
rename to src/pg/sql/03_random_seeds.sql