diff --git a/cmake/utils/add_git_dependency.cmake b/cmake/utils/add_git_dependency.cmake
index 30cec055..e942a0e3 100644
--- a/cmake/utils/add_git_dependency.cmake
+++ b/cmake/utils/add_git_dependency.cmake
@@ -6,6 +6,17 @@ function(add_git_dependency SOURCE_FILE)
         return()
     endif()
 
+    # If we're a submodule, .git won't be a directory
+    if(NOT IS_DIRECTORY ${GIT_DIR})
+        file(READ ${GIT_DIR} GIT_FILE_CONTENT)
+        string(REGEX MATCH "gitdir: (.+)" MATCHED_PATH ${GIT_FILE_CONTENT})
+        if(NOT MATCHED_PATH)
+            return()
+        endif()
+
+        string(STRIP ${CMAKE_MATCH_1} GIT_DIR)
+    endif()
+
     set(GIT_FILES)
     list(APPEND GIT_FILES ${GIT_DIR}/HEAD)
     list(APPEND GIT_FILES ${GIT_DIR}/packed-refs)