diff --git a/changelog.d/20250826_171614_salome.voltz_scrt_5812_investigate_ggshield_running_into_an_ownership_issue_in_git.md b/changelog.d/20250826_171614_salome.voltz_scrt_5812_investigate_ggshield_running_into_an_ownership_issue_in_git.md
new file mode 100644
index 0000000000..6033f2348d
--- /dev/null
+++ b/changelog.d/20250826_171614_salome.voltz_scrt_5812_investigate_ggshield_running_into_an_ownership_issue_in_git.md
@@ -0,0 +1,42 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+For top level release notes, leave all the headers commented out.
+-->
+
+<!--
+### Removed
+
+- A bullet item for the Removed category.
+
+-->
+<!--
+### Added
+
+- A bullet item for the Added category.
+
+-->
+<!--
+### Changed
+
+- A bullet item for the Changed category.
+
+-->
+<!--
+### Deprecated
+
+- A bullet item for the Deprecated category.
+
+-->
+
+### Fixed
+
+- Extend the range of API error status code supported by ggshield so the UI correctly displays them.
+
+<!--
+### Security
+
+- A bullet item for the Security category.
+
+-->
diff --git a/ggshield/core/errors.py b/ggshield/core/errors.py
index 2348912d66..ef79d9a9da 100644
--- a/ggshield/core/errors.py
+++ b/ggshield/core/errors.py
@@ -213,3 +213,7 @@ def handle_api_error(detail: Detail) -> None:
         raise UnexpectedError(f"Scanning failed: {detail.detail}")
     if detail.status_code == 403 and detail.detail == "Quota limit reached.":
         raise QuotaLimitReachedError()
+    if detail.status_code == 400 and "not found" in detail.detail:
+        raise UnexpectedError(detail.detail)
+    if 500 <= detail.status_code < 600:
+        raise ServiceUnavailableError(detail.detail)
diff --git a/ggshield/verticals/secret/secret_scanner.py b/ggshield/verticals/secret/secret_scanner.py
index bfb840ae92..e323eee8ca 100644
--- a/ggshield/verticals/secret/secret_scanner.py
+++ b/ggshield/verticals/secret/secret_scanner.py
@@ -231,7 +231,7 @@ def handle_scan_chunk_error(detail: Detail, chunk: List[Scannable]) -> None:
     details = None
 
     # Handle source_uuid not found error specifically
-    if "Source not found" in detail.detail:
+    if "Source" in detail.detail and "not found" in detail.detail:
         ui.display_error("The provided source was not found in GitGuardian.")
         return
 
diff --git a/tests/unit/verticals/secret/__snapshots__/test_secret_scanner.ambr b/tests/unit/verticals/secret/__snapshots__/test_secret_scanner.ambr
index 48517b1ba9..9fba0b693e 100644
--- a/tests/unit/verticals/secret/__snapshots__/test_secret_scanner.ambr
+++ b/tests/unit/verticals/secret/__snapshots__/test_secret_scanner.ambr
@@ -7,12 +7,6 @@
   
   '''
 # ---
-# name: test_handle_scan_error[source not found]
-  '''
-  Error: The provided source was not found in GitGuardian.
-  
-  '''
-# ---
 # name: test_handle_scan_error[too many documents]
   '''
   Error: Scanning failed. Results may be incomplete.
diff --git a/tests/unit/verticals/secret/test_secret_scanner.py b/tests/unit/verticals/secret/test_secret_scanner.py
index 077975987b..53cba34f1f 100644
--- a/tests/unit/verticals/secret/test_secret_scanner.py
+++ b/tests/unit/verticals/secret/test_secret_scanner.py
@@ -200,21 +200,21 @@ def test_handle_scan_error_api_key():
             ],
             id="single file exception",
         ),
-        pytest.param(
-            Detail("Source not found"),
-            400,
-            [StringScannable(content="test", url="test.txt")],
-            id="source not found",
-        ),
     ],
 )
 def test_handle_scan_error(detail, status_code, chunk, capsys, snapshot):
-    detail.status_code = 400
+    detail.status_code = status_code
     handle_scan_chunk_error(detail, chunk)
     captured = capsys.readouterr()
     assert captured.err == snapshot
 
 
+def test_scan_source_uuid_not_found():
+    detail = Detail(detail="Source not found.", status_code=400)
+    with pytest.raises(UnexpectedError):
+        handle_scan_chunk_error(detail, Mock())
+
+
 def test_handle_scan_quota_limit_reached():
     detail = Detail(detail="Quota limit reached.", status_code=403)
     with pytest.raises(QuotaLimitReachedError):