SemanticException Partition spec {p1=null, p2=null} contains non-partition columns

[Buntu Dev]

I'm running into this error while doing a dynamic partition insert. Heres
how I created the table:

~~~~
CREATE TABLE `part_table`(
  `c1` bigint,
  `c2` bigint,
  `c3` bigint)
PARTITIONED BY (p1 string, `p2` string)
STORED AS PARQUET;

~~~~

Here is the insert table:

~~~~
SET hive.exec.dynamic.partition = true;
SET hive.exec.dynamic.partition.mode = nonstrict;

insert overwrite table part_table partition(p1, p2)
select c1 as c1,
  c2 as c2,
  c3 as c3,
  regexp_replace(date_col, '-', '') as p1,
  p2 as p2
from src_table;
~~~~

I'm using Hive 1.1.0 on CDH 5.4.2. Can anyone let me know what else is
missing?

Thanks!