1 files changed, 6 insertions, 2 deletions

diff --git a/externals/cmake-modules/GetGitRevisionDescription.cmake.in b/externals/cmake-modules/GetGitRevisionDescription.cmake.in
index 888ce13aa..0d7eb3c26 100644
--- a/externals/cmake-modules/GetGitRevisionDescription.cmake.in
+++ b/externals/cmake-modules/GetGitRevisionDescription.cmake.in
@@ -33,6 +33,10 @@ else()
 endif()
 
 if(NOT HEAD_HASH)
-        file(READ "@GIT_DATA@/head-ref" HEAD_HASH LIMIT 1024)
-        string(STRIP "${HEAD_HASH}" HEAD_HASH)
+        if(EXISTS "@GIT_DATA@/head-ref")
+                file(READ "@GIT_DATA@/head-ref" HEAD_HASH LIMIT 1024)
+                string(STRIP "${HEAD_HASH}" HEAD_HASH)
+        else()
+                set(HEAD_HASH "Unknown")
+        endif()
 endif()