diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 74631d5d..ae0ef693 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -32,6 +32,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
         with:
+          submodules: true
           fetch-depth: 0
 
       - name: Show github context
@@ -75,6 +76,7 @@ jobs:
       - name: Checkout into dir1
         uses: actions/checkout@v2
         with:
+          submodules: true
           fetch-depth: 0
           path: dir1
       - name: Run changed-files with defaults on the dir1
@@ -97,6 +99,7 @@ jobs:
       - name: Checkout into dir2
         uses: actions/checkout@v2
         with:
+          submodules: true
           fetch-depth: 0
           path: dir2
       - name: Run changed-files with defaults on the dir2
@@ -207,6 +210,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
         with:
+          submodules: true
           fetch-depth: 0
       - name: Run changed-files with defaults
         id: changed-files
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 00000000..b0a35949
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "test/demo"]
+	path = test/demo
+	url = git@github.com:tj-actions/demo.git
diff --git a/entrypoint.sh b/entrypoint.sh
index 80f4b553..4d9efb77 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -2,6 +2,25 @@
 
 set -eu
 
+function get_diff() {
+  base="$1"
+  sha="$2"
+  filter="$3"
+  while IFS='' read -r sub; do
+    sub_commit_pre="$(git diff "$base" "$sha" -- "$sub" | grep '^[-]Subproject commit' | sed 's/[-]Subproject commit //')"
+    sub_commit_cur="$(git diff "$base" "$sha" -- "$sub" | grep '^[+]Subproject commit' | sed 's/[+]Subproject commit //')"
+    if [ -n "$sub_commit_cur" ]; then
+    (
+      cd "$sub" && (
+        # the strange magic number is a hardcoded "empty tree" commit sha
+        get_diff "${sub_commit_pre:-4b825dc642cb6eb9a060e54bf8d69288fbee4904}" "${sub_commit_cur}" "$filter" | sed "s#^#$sub/#"
+      )
+    )
+    fi
+  done < <(git submodule | awk '{print $2}')
+  git diff --diff-filter="$filter" --name-only --ignore-submodules=all "$base" "$sha"
+}
+
 echo "::group::changed-files"
 
 echo "Resolving repository path..."
@@ -20,34 +39,34 @@ echo "Retrieving changes between $INPUT_PREVIOUS_SHA ($INPUT_TARGET_BRANCH) →
 echo "Getting diff..."
 
 if [[ -z "$INPUT_FILES_PATTERN" ]]; then
-  ADDED=$(git diff --submodule=diff --diff-filter=A --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  COPIED=$(git diff --submodule=diff --diff-filter=C --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  DELETED=$(git diff --submodule=diff --diff-filter=D --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  MODIFIED=$(git diff --submodule=diff --diff-filter=M --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  RENAMED=$(git diff --submodule=diff --diff-filter=R --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  TYPE_CHANGED=$(git diff --submodule=diff --diff-filter=T --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  UNMERGED=$(git diff --submodule=diff --diff-filter=U --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  UNKNOWN=$(git diff --submodule=diff --diff-filter=X --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_CHANGED_AND_MODIFIED=$(git diff --submodule=diff --diff-filter="*ACDMRTUX" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_CHANGED=$(git diff --submodule=diff --diff-filter="ACMR" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_MODIFIED=$(git diff --submodule=diff --diff-filter="ACMRD" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  ADDED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" A | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  COPIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" C | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  DELETED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" D | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" M | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  RENAMED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" R | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  TYPE_CHANGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" T | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  UNMERGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" U | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  UNKNOWN=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" X | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_CHANGED_AND_MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "*ACDMRTUX" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_CHANGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "ACMR" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "ACMRD" | awk -v d="$INPUT_SEPARATOR" '{s=(NR==1?s:s d)$0}END{print s}')
 else
   echo "Input files pattern: $INPUT_FILES_PATTERN"
   FILES_PATTERN="^($INPUT_FILES_PATTERN)$"
 
-  ADDED=$(git diff --submodule=diff --diff-filter=A --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  COPIED=$(git diff --submodule=diff --diff-filter=C --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  DELETED=$(git diff --submodule=diff --diff-filter=D --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  MODIFIED=$(git diff --submodule=diff --diff-filter=M --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  RENAMED=$(git diff --submodule=diff --diff-filter=R --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  TYPE_CHANGED=$(git diff --submodule=diff --diff-filter=T --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  UNMERGED=$(git diff --submodule=diff --diff-filter=U --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  UNKNOWN=$(git diff --submodule=diff --diff-filter=X --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_CHANGED_AND_MODIFIED=$(git diff --submodule=diff --diff-filter="*ACDMRTUX" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_CHANGED=$(git diff --submodule=diff --diff-filter="ACMR" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
-  ALL_MODIFIED=$(git diff --submodule=diff --diff-filter="ACMRD" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  ADDED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" A | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  COPIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" C | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  DELETED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" D | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" M | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  RENAMED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" R | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  TYPE_CHANGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" T | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  UNMERGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" U | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  UNKNOWN=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" X | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_CHANGED_AND_MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "*ACDMRTUX" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_CHANGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "ACMR" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_MODIFIED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "ACMRD" | grep -E "$FILES_PATTERN" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
 
-  ALL_OTHER_CHANGED=$(git diff --submodule=diff --diff-filter="ACMR" --name-only "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
+  ALL_OTHER_CHANGED=$(get_diff "$INPUT_PREVIOUS_SHA" "$INPUT_CURRENT_SHA" "ACMR" | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
   UNIQUE_ALL_CHANGED=$(echo "${ALL_CHANGED}" | awk '{gsub(/\|/,"\n"); print $0;}' | awk '!a[$0]++' | awk -v d="|" '{s=(NR==1?s:s d)$0}END{print s}')
 
   if [[ -n "${UNIQUE_ALL_CHANGED}" ]]; then
diff --git a/test/demo b/test/demo
new file mode 160000
index 00000000..82fc87d8
--- /dev/null
+++ b/test/demo
@@ -0,0 +1 @@
+Subproject commit 82fc87d8654c49fa7773a2d51e5681173b10e13d