diff --git a/.github/workflows/element-web.yaml b/.github/workflows/element-web.yaml
index 022c293abe..e08803c216 100644
--- a/.github/workflows/element-web.yaml
+++ b/.github/workflows/element-web.yaml
@@ -15,10 +15,11 @@ on:
 concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
     cancel-in-progress: true
+
 env:
-    # These must be set for fetchdep.sh to get the right branch
-    REPOSITORY: ${{ github.repository }}
+    # fetchdep.sh needs to know our PR number
     PR_NUMBER: ${{ github.event.pull_request.number }}
+
 jobs:
     build:
         name: "Build Element-Web"
diff --git a/.github/workflows/static_analysis.yaml b/.github/workflows/static_analysis.yaml
index b95fc3b1c8..c4bf0ef3be 100644
--- a/.github/workflows/static_analysis.yaml
+++ b/.github/workflows/static_analysis.yaml
@@ -10,10 +10,11 @@ on:
 concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
     cancel-in-progress: true
+
 env:
-    # These must be set for fetchdep.sh to get the right branch
-    REPOSITORY: ${{ github.repository }}
+    # fetchdep.sh needs to know our PR number
     PR_NUMBER: ${{ github.event.pull_request.number }}
+
 jobs:
     ts_lint:
         name: "Typescript Syntax Check"
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index bdc1badd6a..ad8fdab8c7 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -20,11 +20,12 @@ on:
 concurrency:
     group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
     cancel-in-progress: true
+
 env:
     ENABLE_COVERAGE: ${{ github.event_name != 'merge_group' && inputs.disable_coverage != 'true' }}
-    # These must be set for fetchdep.sh to get the right branch
-    REPOSITORY: ${{ github.repository }}
+    # fetchdep.sh needs to know our PR number
     PR_NUMBER: ${{ github.event.pull_request.number }}
+
 jobs:
     jest:
         name: Jest
diff --git a/scripts/fetchdep.sh b/scripts/fetchdep.sh
index 81f0784ff9..3a8b9be4dd 100755
--- a/scripts/fetchdep.sh
+++ b/scripts/fetchdep.sh
@@ -10,8 +10,15 @@ defbranch="$3"
 
 rm -r "$defrepo" || true
 
-PR_ORG=${PR_ORG:-"matrix-org"}
-PR_REPO=${PR_REPO:-"matrix-react-sdk"}
+# figure out where to look for pull requests:
+#   - We may have been told an explicit repo via the PR_ORG/PR_REPO/PR_NUMBER env vars
+#   - otherwise, check the $GITHUB_ env vars which are set by Github Actions
+#   - failing that, fall back to the matrix-org/matrix-react-sdk repo.
+#
+# in ether case, the PR_NUMBER variable must be set explicitly.
+default_org_repo=${GITHUB_REPOSITORY:-"matrix-org/matrix-react-sdk"}
+PR_ORG=${PR_ORG:-${default_org_repo%%/*}}
+PR_REPO=${PR_REPO:-${default_org_repo##*/}}
 
 # A function that clones a branch of a repo based on the org, repo and branch
 clone() {