diff --git a/lisp/ob-python.el b/lisp/ob-python.el
index dbcfac08d..fbc4e969f 100644
--- a/lisp/ob-python.el
+++ b/lisp/ob-python.el
@@ -82,10 +82,14 @@ This function is called by `org-babel-execute-src-block'."
 	 (return-val (when (and (eq result-type 'value) (not session))
 		       (cdr (assq :return params))))
 	 (preamble (cdr (assq :preamble params)))
+	 (preamble (concat preamble (and preamble "\n")
+			   (mapconcat #'identity
+				      (org-babel-variable-assignments:python params)
+				      "\n")))
          (full-body
 	  (org-babel-expand-body:generic
 	   (concat body (if return-val (format "\nreturn %s" return-val) ""))
-	   params (org-babel-variable-assignments:python params)))
+	   params))
          (result (org-babel-python-evaluate
 		  session full-body result-type result-params preamble)))
     (org-babel-reassemble-table
@@ -272,7 +276,8 @@ except Exception:
   "Evaluate BODY as Python code."
   (if session
       (org-babel-python-evaluate-session
-       session body result-type result-params)
+       session (concat preamble (and preamble "\n") body)
+       result-type result-params)
     (org-babel-python-evaluate-external-process
      body result-type result-params preamble)))