diff --git a/quit/web/modules/endpoint.py b/quit/web/modules/endpoint.py
index 58b8ccd8..690b7b45 100644
--- a/quit/web/modules/endpoint.py
+++ b/quit/web/modules/endpoint.py
@@ -160,6 +160,22 @@ def sparql(branch_or_ref):
                 else:
                     response.headers["X-CurrentCommit"] = commitid
                 return response
+            except KeyError as e:
+                logger.exception(e)
+                if "config value 'user.name' was not found" in e.args:
+                    message = ("Unable to process query: "
+                               "git config value 'user.name' was not found.\n"
+                               "Pls use the following command in your data repo:"
+                               "\n\n  git config user.name <your name>")
+                    return make_response(message, 400)
+                if "config value 'user.email' was not found" in e.args:
+                    message = ("Unable to process query: "
+                               "git config value 'user.name' was not found.\n"
+                               "Pls use the following command in your data repo:"
+                               "\n\n  git config user.email <your email>")
+                    return make_response(message, 400)
+                # KeyError has many sources -> it could be caused by other problems
+                return make_response('Error after executing the update query.', 400)
             except Exception as e:
                 # query ok, but unsupported query type or other problem during commit
                 logger.exception(e)
diff --git a/quit/web/modules/git.py b/quit/web/modules/git.py
index b59928ee..c28a4975 100644
--- a/quit/web/modules/git.py
+++ b/quit/web/modules/git.py
@@ -258,7 +258,21 @@ def merge(refspec):
             return response
         else:
             return "<pre>Unsupported Mimetype: {}</pre>".format(mimetype), 406
-
+    except KeyError as e:
+        message = "\n"
+        if "config value 'user.name' was not found" in e.args:
+            message += ("Unable to process query: "
+                        "git config value 'user.name' was not found.\n"
+                        "Pls use the following command in your data repo:"
+                        "\n\n  git config user.name <your name>")
+        if "config value 'user.email' was not found" in e.args:
+            message += ("Unable to process query: "
+                        "git config value 'user.name' was not found.\n"
+                        "Pls use the following command in your data repo:"
+                        "\n\n  git config user.email <your email>")
+        logger.error(e)
+        logger.error(traceback.format_exc())
+        return "<pre>" + traceback.format_exc() + message + "</pre>", 400
     except Exception as e:
         logger.error(e)
         logger.error(traceback.format_exc())