diff --git a/splitgill/diffing.py b/splitgill/diffing.py
index fb1a658..26a4d6f 100644
--- a/splitgill/diffing.py
+++ b/splitgill/diffing.py
@@ -102,11 +102,23 @@ def prepare_field_name(name: Any) -> str:
         - convert the name to a str, MongoDB only accepts str keys in objects
         - remove any control characters from the str
         - replace . with _ as Elasticsearch doesn't like dots in keys
+        - replace ^ with _ as this is a reserved character we use in parsed field names
+
+    If after cleaning, the field name is an empty string, we return an underscore.
 
     :param name: the field name
     :return: a clean str field name
     """
-    return invalid_key_char_regex.sub("", str(name)).replace(".", "_").strip()
+    clean_name = (
+        invalid_key_char_regex.sub("", str(name))
+        .replace(".", "_")
+        .replace("^", "_")
+        .strip()
+    )
+    # if this results in the empty string, replace with an underscore
+    if not clean_name:
+        clean_name = "_"
+    return clean_name
 
 
 class DiffOp(NamedTuple):
diff --git a/splitgill/indexing/fields.py b/splitgill/indexing/fields.py
index 46884d2..f0d15a7 100644
--- a/splitgill/indexing/fields.py
+++ b/splitgill/indexing/fields.py
@@ -8,21 +8,6 @@
 from strenum import LowercaseStrEnum, StrEnum
 
 
-def is_field_valid(name: str) -> bool:
-    """
-    Defines a valid field in user provided data.
-
-    :param name: the field name
-    :return: True if the field is valid, False otherwise
-    """
-    # todo: should we disallow fields that have a __ in them for elasticsearch-dsl?
-    # ^ is used in parsed type field names, and we use . in the parsed and data type
-    # fields. Additionally, using dots in names is probably going to result in confusing
-    # outcomes for users given elasticsearch will interpret them as flattened objects
-    # and expand them out
-    return name and "^" not in name and "." not in name
-
-
 class DocumentField(LowercaseStrEnum):
     """
     Enum representing the fields used in the indexed documents.
diff --git a/tests/indexing/test_fields.py b/tests/indexing/test_fields.py
index fc1ee78..78b8f80 100644
--- a/tests/indexing/test_fields.py
+++ b/tests/indexing/test_fields.py
@@ -6,7 +6,6 @@
 from splitgill.indexing.fields import (
     ParsedType,
     parsed_path,
-    is_field_valid,
     DocumentField,
     DataType,
     DataField,
@@ -14,14 +13,6 @@
 )
 
 
-def test_is_field_valid():
-    assert is_field_valid("egg")
-    assert is_field_valid("_egg")
-    assert not is_field_valid("")
-    assert not is_field_valid("egg^beans")
-    assert not is_field_valid("egg.beans")
-
-
 @pytest.mark.parametrize("parsed_type", ParsedType)
 def test_parsed_path(parsed_type: ParsedType):
     field = "a.field.in.the.record"
diff --git a/tests/test_diffing.py b/tests/test_diffing.py
index dc13c9e..a5213df 100644
--- a/tests/test_diffing.py
+++ b/tests/test_diffing.py
@@ -132,6 +132,12 @@ def test_prepare_field_name():
     assert prepare_field_name(".x.y.z.1.2.") == "_x_y_z_1_2_"
     # a mix of horrors
     assert prepare_field_name("\nx.\ty\r  \x07fowien") == "x_y  fowien"
+    # a ^
+    assert prepare_field_name("x^y") == "x_y"
+    # an empty name
+    assert prepare_field_name("") == "_"
+    # a name which becomes empty after removing all the junk
+    assert prepare_field_name("   \t   \x07   ") == "_"
 
 
 class TestDiff: