diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 2d1ede46be0..526f9d789e5 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3920,7 +3920,14 @@ exec_eval_expr(PLpgSQL_execstate *estate,
 	 * directly
 	 */
 	if (expr->expr_simple_expr != NULL)
-		return exec_eval_simple_expr(estate, expr, isNull, rettype);
+	{
+		/*
+		 * If expression is in use in current xact, don't touch it.
+		 */
+		if (!(expr->expr_simple_in_use &&
+			  expr->expr_simple_id == estate->eval_estate_simple_id))
+			return exec_eval_simple_expr(estate, expr, isNull, rettype);
+	}
 
 	rc = exec_run_select(estate, expr, 2, NULL);
 	if (rc != SPI_OK_SELECT)
@@ -4071,6 +4078,7 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
 	{
 		expr->expr_simple_state = ExecPrepareExpr(expr->expr_simple_expr,
 												  estate->eval_estate);
+		expr->expr_simple_in_use = false;
 		expr->expr_simple_id = estate->eval_estate_simple_id;
 	}
 
@@ -4130,6 +4138,11 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
 			ActiveSnapshot = CopySnapshot(GetTransactionSnapshot());
 		}
 
+		/*
+		 * Mark expression as busy for the duration of the ExecEvalExpr call.
+		 */
+		expr->expr_simple_in_use = true;
+
 		/*
 		 * Finally we can call the executor to evaluate the expression
 		 */
@@ -4137,11 +4150,15 @@ exec_eval_simple_expr(PLpgSQL_execstate *estate,
 							  econtext,
 							  isNull,
 							  NULL);
+
+		/* Assorted cleanup */
+		expr->expr_simple_in_use = false;
 		MemoryContextSwitchTo(oldcontext);
 	}
 	PG_CATCH();
 	{
 		/* Restore global vars and propagate error */
+		/* note we intentionally don't reset expr_simple_in_use here */
 		ActiveSnapshot = saveActiveSnapshot;
 		PG_RE_THROW();
 	}
@@ -4741,6 +4758,7 @@ exec_simple_check_plan(PLpgSQL_expr *expr)
 	 */
 	expr->expr_simple_expr = tle->expr;
 	expr->expr_simple_state = NULL;
+	expr->expr_simple_in_use = false;
 	expr->expr_simple_id = -1;
 	/* Also stash away the expression result type */
 	expr->expr_simple_type = exprType((Node *) tle->expr);
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index c48a66a1912..12790e9aceb 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -181,10 +181,11 @@ typedef struct PLpgSQL_expr
 
 	/*
 	 * if expr is simple AND prepared in current eval_estate,
-	 * expr_simple_state is valid.  Test validity by seeing if expr_simple_id
-	 * matches eval_estate_simple_id.
+	 * expr_simple_state and expr_simple_in_use are valid. Test validity by
+	 * seeing if expr_simple_id matches eval_estate_simple_id.
 	 */
-	ExprState  *expr_simple_state;
+	ExprState  *expr_simple_state;		/* eval tree for expr_simple_expr */
+	bool		expr_simple_in_use;		/* true if eval tree is active */
 	long int	expr_simple_id;
 
 	/* params to pass to expr */
diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index f2826f10625..ff1a9604df7 100644
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -2977,3 +2977,50 @@ SELECT nonsimple_expr_test();
 (1 row)
 
 DROP FUNCTION nonsimple_expr_test();
+--
+-- Test cases involving recursion and error recovery in simple expressions
+-- (bugs in all versions before October 2010).  The problems are most
+-- easily exposed by mutual recursion between plpgsql and sql functions.
+--
+create function recurse(float8) returns float8 as
+$$
+begin
+  if ($1 < 10) then
+    return sql_recurse($1 + 1);
+  else
+    return $1;
+  end if;
+end;
+$$ language plpgsql;
+-- "limit" is to prevent this from being inlined
+create function sql_recurse(float8) returns float8 as
+$$ select recurse($1) limit 1; $$ language sql;
+select recurse(0);
+ recurse 
+---------
+      10
+(1 row)
+
+create function error1(text) returns text language sql as
+$$ SELECT relname::text FROM pg_class c WHERE c.oid = $1::regclass $$;
+create function error2(p_name_table text) returns text language plpgsql as $$
+begin
+  return error1(p_name_table);
+end$$;
+BEGIN;
+create table public.stuffs (stuff text);
+SAVEPOINT a;
+select error2('nonexistent.stuffs');
+ERROR:  schema "nonexistent" does not exist
+CONTEXT:  SQL function "error1" statement 1
+PL/pgSQL function "error2" line 2 at return
+ROLLBACK TO a;
+select error2('public.stuffs');
+ error2 
+--------
+ stuffs
+(1 row)
+
+rollback;
+drop function error2(p_name_table text);
+drop function error1(text);
diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index 27ab5afbdff..37bdb72fb7e 100644
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -2480,3 +2480,45 @@ $$ LANGUAGE plpgsql;
 SELECT nonsimple_expr_test();
 
 DROP FUNCTION nonsimple_expr_test();
+
+--
+-- Test cases involving recursion and error recovery in simple expressions
+-- (bugs in all versions before October 2010).  The problems are most
+-- easily exposed by mutual recursion between plpgsql and sql functions.
+--
+
+create function recurse(float8) returns float8 as
+$$
+begin
+  if ($1 < 10) then
+    return sql_recurse($1 + 1);
+  else
+    return $1;
+  end if;
+end;
+$$ language plpgsql;
+
+-- "limit" is to prevent this from being inlined
+create function sql_recurse(float8) returns float8 as
+$$ select recurse($1) limit 1; $$ language sql;
+
+select recurse(0);
+
+create function error1(text) returns text language sql as
+$$ SELECT relname::text FROM pg_class c WHERE c.oid = $1::regclass $$;
+
+create function error2(p_name_table text) returns text language plpgsql as $$
+begin
+  return error1(p_name_table);
+end$$;
+
+BEGIN;
+create table public.stuffs (stuff text);
+SAVEPOINT a;
+select error2('nonexistent.stuffs');
+ROLLBACK TO a;
+select error2('public.stuffs');
+rollback;
+
+drop function error2(p_name_table text);
+drop function error1(text);