diff --git a/.github/workflows/nim-matrix.yml b/.github/workflows/nim-matrix.yml
index 0b57c8bf..579ee6a5 100644
--- a/.github/workflows/nim-matrix.yml
+++ b/.github/workflows/nim-matrix.yml
@@ -6,7 +6,7 @@ on:
 
 env:
   cache_nonce: 0 # Allows for easily busting actions/cache caches
-  nim_version: pinned, v1.6.16, v1.6.18
+  nim_version: pinned
 
 jobs:
   matrix:
diff --git a/Makefile b/Makefile
index 2e1f97ad..54ac04d2 100644
--- a/Makefile
+++ b/Makefile
@@ -15,7 +15,7 @@
 #
 # If NIM_COMMIT is set to "nimbusbuild", this will use the
 # version pinned by nimbus-build-system.
-PINNED_NIM_VERSION := v1.6.14
+PINNED_NIM_VERSION := 38640664088251bbc88917b4bacfd86ec53014b8 # 1.6.21
 
 ifeq ($(NIM_COMMIT),)
 NIM_COMMIT := $(PINNED_NIM_VERSION)