diff --git a/master_changes.md b/master_changes.md
index e9d9f2ab7aa..7dcc5bb41b5 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -86,6 +86,7 @@ users)
 ## Sandbox
 
 ## VCS
+  * Fail when git submodule fails to update instead of showing a warning and ignoring the error [#6132 @kit-ty-kate - fix #6131]
 
 ## Build
  * Synchronise opam-core.opam with opam-repository changes [#6043 @dra27]
diff --git a/src/repository/opamGit.ml b/src/repository/opamGit.ml
index 49980641c77..1b2f4c565df 100644
--- a/src/repository/opamGit.ml
+++ b/src/repository/opamGit.ml
@@ -179,9 +179,7 @@ module VCS : OpamVCS.VCS = struct
       if OpamFilename.exists (repo_root // ".gitmodules") then
         git repo_root [ "submodule"; "update"; "--init"; "--recursive" ]
         @@> fun r ->
-        if OpamProcess.is_failure r then
-          OpamConsole.warning "Git submodule update failed in %s"
-            (OpamFilename.Dir.to_string repo_root);
+        OpamSystem.raise_on_process_error r;
         Done ()
       else Done ()
 
diff --git a/tests/reftests/git.test b/tests/reftests/git.test
index ca50d5a0f2c..af61d7b0f80 100644
--- a/tests/reftests/git.test
+++ b/tests/reftests/git.test
@@ -59,22 +59,17 @@ The following actions will be performed:
 
 <><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 Processing  1/3: [submodule.1: git]
-[WARNING] Git submodule update failed in ${BASEDIR}/OPAM/submodule/.opam-switch/sources/submodule.1
--> retrieved submodule.1  (git+file://${BASEDIR}/use-submodule)
-Processing  2/3: [submodule: ls]
-+ ${BASEDIR}/OPAM/opam-init/hooks/sandbox.sh "build" "ls" "vendor/some-file" (CWD=${BASEDIR}/OPAM/submodule/.opam-switch/build/submodule.1)
-- ls: cannot access 'vendor/some-file': No such file or directory
-[ERROR] The compilation of submodule.1 failed at "ls vendor/some-file".
-
-##% output ###
-# ls: cannot access 'vendor/some-file': No such file or directory
+[ERROR] Could not synchronize ${BASEDIR}/OPAM/submodule/.opam-switch/sources/submodule.1 from "git+file://${BASEDIR}/use-submodule":
+        "/usr/bin/git submodule update --init --recursive" exited with code 1
+[ERROR] Failed to get sources of submodule.1: git+file://${BASEDIR}/use-submodule
 
+OpamSolution.Fetch_fail("git+file://${BASEDIR}/use-submodule")
 
 
 <><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 +- The following actions failed
-| - build submodule 1
+| - fetch submodule 1
 +- 
 - No changes have been performed
 '${OPAM} install --verbose submodule' failed.
-# Return code 31 #
+# Return code 40 #