diff --git a/.github/workflows/auto_pr_test.yml b/.github/workflows/auto_pr_test.yml
index 7fbca45f..50db08ac 100644
--- a/.github/workflows/auto_pr_test.yml
+++ b/.github/workflows/auto_pr_test.yml
@@ -14,7 +14,7 @@ jobs:
   # This job builds the box model and runs our test suite.
   build:
     runs-on: ${{ matrix.os }}
-    container: coherellc/tdycore-petsc:latest
+    container: coherellc/tdycore-petsc:c29323cac9f
 
     # A build matrix storing all desired configurations.
     strategy:
diff --git a/README.md b/README.md
index 817e80ed..45464cf1 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,14 @@ TDycores provides two dynamical cores:
 Both dycores can use meshes with hexahedral or triangular prismatic cells
 with planar faces. The prismatic cells are aligned logically along a z axis.
 
+## Dependencies
+
+`TDycore` uses [PETSc](https://petsc.org/release/), tracking the
+[main branch](https://gitlab.com/petsc/petsc) fairly closely. Currently,
+`TDycore` is tested against revision `c29323cac9f`.
+
+## More information
+
 Check out the [Wiki](https://github.com/TDycores-Project/TDycore/wiki) for
 documentation, including instructions for
 [building and installing TDycore](https://github.com/TDycores-Project/TDycore/wiki/Building-and-Installing-TDycore).
diff --git a/include/tdytimers.h b/include/tdytimers.h
index 7e7cfda8..70c52a2c 100644
--- a/include/tdytimers.h
+++ b/include/tdytimers.h
@@ -19,7 +19,7 @@ PETSC_EXTERN PetscErrorCode TDyEnableTimers(void);
 
 // To accomplish this, we use a hash map with string keys and PetscLogEvent
 // values. PETSc ships with khash, so let's appropriate it.
-#include <petsc/private/kernels/khash.h>
+#include <petsc/private/khash/khash.h>
 KHASH_MAP_INIT_STR(TDY_TIMER_MAP, PetscLogEvent)
 PETSC_EXTERN khash_t(TDY_TIMER_MAP)* TDY_TIMERS;
 
diff --git a/tools/build-petsc-docker-image.sh b/tools/build-petsc-docker-image.sh
index 4af8c903..ebe4f1fe 100755
--- a/tools/build-petsc-docker-image.sh
+++ b/tools/build-petsc-docker-image.sh
@@ -19,7 +19,7 @@ fi
 
 DOCKERHUB_USER=coherellc
 IMAGE_NAME=tdycore-petsc
-TAG=latest
+TAG=$PETSC_HASH
 
 # Build the image locally.
 mkdir -p docker-build