diff --git a/build-constraints.yaml b/build-constraints.yaml
index 237d4610..89079083 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -2796,7 +2796,7 @@ packages:
 
     "Kadzuya Okamoto <arow.okamoto@gmail.com> @arowM":
         - type-level-kv-list
-        # - heterocephalus # build failure with ghc 8.4 https://github.com/arowM/heterocephalus/issues/22
+        - heterocephalus
         - bookkeeping
         - ochintin-daicho
 
@@ -3286,7 +3286,6 @@ packages:
         - hashtables < 0 # build failure with GHC 8.4 https://github.com/gregorycollins/hashtables/issues/45
         - haskell-neo4j-client < 0 # build failure with GHC 8.4 https://github.com/asilvestre/haskell-neo4j-rest-client/issues/32
         - heap < 0 # build failure with GHC 8.4 https://github.com/pruvisto/heap/issues/5
-        - heterocephalus < 0 # build failure with GHC 8.4 https://github.com/arowM/heterocephalus/issues/22
         - hpqtypes < 0 # build failure with GHC 8.4 https://github.com/scrive/hpqtypes/issues/7
         - hspec-webdriver < 0 # https://bitbucket.org/wuzzeb/webdriver-utils/issues/9/hspec-webdriver-build-failure-with-ghc-84
         - hw-fingertree-strict < 0 # build failure with GHC 8.4 https://hub.darcs.net/ross/fingertree/issue/5
@@ -4312,7 +4311,6 @@ packages:
         - modify-fasta < 0 # GHC 8.4 via fasta
         - blosum < 0 # GHC 8.4 via pipes-text
         - modify-fasta < 0 # GHC 8.4 via pipes-text
-        - xml-html-qq < 0 # GHC 8.4 via heterocephalus
         - Spock < 0 # GHC 8.4 via list-t
         - Spock < 0 # GHC 8.4 via stm-containers
         - Spock-worker < 0 # GHC 8.4 via Spock