diff --git a/haystack/document_stores/types/filter_policy.py b/haystack/document_stores/types/filter_policy.py
index 786c30767d..4825ac31ec 100644
--- a/haystack/document_stores/types/filter_policy.py
+++ b/haystack/document_stores/types/filter_policy.py
@@ -81,6 +81,19 @@ def convert_logical_operators(filter_dict: Dict[str, Any]) -> Dict[str, Any]:
     return filter_dict
 
 
+def logical_operators_to_str(filter_dict: Dict[str, Any]) -> Dict[str, Any]:
+    """
+    Convert any logical operators found in a filter dictionary to string.
+
+    :param filter_dict: A dictionary representing a filter with potential LogicalOperator enums.
+    :return: A new dictionary with LogicalOperator strings in place of enums.
+    """
+    # If the dictionary represents a logical filter, update the 'operator'
+    if is_logical_filter(filter_dict) and isinstance(filter_dict["operator"], LogicalOperator):
+        filter_dict["operator"] = filter_dict["operator"].value
+    return filter_dict
+
+
 def is_comparison_filter(filter_item: Dict[str, Any]) -> bool:
     """
     Check if the given filter is a comparison filter.
@@ -340,16 +353,23 @@ def apply_filter_policy(
         runtime_filters = convert_logical_operators(runtime_filters)
         # now we merge filters
         if is_comparison_filter(init_filters) and is_comparison_filter(runtime_filters):
-            return combine_two_comparison_filters(init_filters, runtime_filters, default_logical_operator)
+            combined_filters = combine_two_comparison_filters(init_filters, runtime_filters, default_logical_operator)
+            return logical_operators_to_str(combined_filters)
         elif is_comparison_filter(init_filters) and is_logical_filter(runtime_filters):
-            return combine_init_comparison_and_runtime_logical_filters(
+            combined_filters = combine_init_comparison_and_runtime_logical_filters(
                 init_filters, runtime_filters, default_logical_operator
             )
+            return logical_operators_to_str(combined_filters)
         elif is_logical_filter(init_filters) and is_comparison_filter(runtime_filters):
-            return combine_runtime_comparison_and_init_logical_filters(
+            combined_filters = combine_runtime_comparison_and_init_logical_filters(
                 runtime_filters, init_filters, default_logical_operator
             )
+            return logical_operators_to_str(combined_filters)
         elif is_logical_filter(init_filters) and is_logical_filter(runtime_filters):
-            return combine_two_logical_filters(init_filters, runtime_filters)
+            combined_filters = combine_two_logical_filters(init_filters, runtime_filters)
+            return logical_operators_to_str(combined_filters)
 
-    return runtime_filters or init_filters
+    resulting_filter = runtime_filters or init_filters
+    if resulting_filter:
+        resulting_filter = logical_operators_to_str(resulting_filter)
+    return resulting_filter
diff --git a/test/document_stores/test_filter_policy.py b/test/document_stores/test_filter_policy.py
index abe761ddac..26ad193759 100644
--- a/test/document_stores/test_filter_policy.py
+++ b/test/document_stores/test_filter_policy.py
@@ -45,7 +45,7 @@ def test_merge_two_comparison_filters():
     runtime_filters = {"field": "meta.type", "operator": "==", "value": "article"}
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
     assert result == {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.date", "operator": ">=", "value": "2015-01-01"},
             {"field": "meta.type", "operator": "==", "value": "article"},
@@ -60,7 +60,7 @@ def test_merge_init_comparison_and_runtime_logical_filters():
     """
     init_filters = {"field": "meta.date", "operator": ">=", "value": "2015-01-01"}
     runtime_filters = {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -68,7 +68,7 @@ def test_merge_init_comparison_and_runtime_logical_filters():
     }
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
     assert result == {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -99,7 +99,7 @@ def test_merge_runtime_comparison_and_init_logical_filters_with_string_operators
     }
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
     assert result == {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -115,7 +115,7 @@ def test_merge_runtime_comparison_and_init_logical_filters():
     Result: AND operator with both filters
     """
     init_filters = {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -124,7 +124,7 @@ def test_merge_runtime_comparison_and_init_logical_filters():
     runtime_filters = {"field": "meta.date", "operator": ">=", "value": "2015-01-01"}
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
     assert result == {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -139,14 +139,14 @@ def test_merge_two_logical_filters():
     Result: AND operator with both filters
     """
     init_filters = {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
         ],
     }
     runtime_filters = {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.genre", "operator": "IN", "value": ["economy", "politics"]},
             {"field": "meta.publisher", "operator": "==", "value": "nytimes"},
@@ -154,7 +154,7 @@ def test_merge_two_logical_filters():
     }
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
     assert result == {
-        "operator": LogicalOperator.AND,
+        "operator": "AND",
         "conditions": [
             {"field": "meta.type", "operator": "==", "value": "article"},
             {"field": "meta.rating", "operator": ">=", "value": 3},
@@ -171,7 +171,7 @@ def test_merge_with_different_logical_operators():
     """
     init_filters = {"operator": "AND", "conditions": [{"field": "meta.type", "operator": "==", "value": "article"}]}
     runtime_filters = {
-        "operator": LogicalOperator.OR,
+        "operator": "OR",
         "conditions": [{"field": "meta.genre", "operator": "IN", "value": ["economy", "politics"]}],
     }
     result = apply_filter_policy(FilterPolicy.MERGE, init_filters, runtime_filters)
@@ -204,7 +204,7 @@ def test_merge_with_custom_logical_operator(logical_operator):
         default_logical_operator=LogicalOperator.from_str(logical_operator),
     )
     assert result == {
-        "operator": LogicalOperator.from_str(logical_operator),
+        "operator": logical_operator,
         "conditions": [
             {"field": "meta.date", "operator": ">=", "value": "2015-01-01"},
             {"field": "meta.type", "operator": "==", "value": "article"},