diff --git a/ingest_test.go b/ingest_test.go
index 637a78d5e2..b4f34a2d65 100644
--- a/ingest_test.go
+++ b/ingest_test.go
@@ -1897,16 +1897,21 @@ func TestIngestExternal(t *testing.T) {
 
 func TestIngestMemtableOverlaps(t *testing.T) {
 	comparers := []Comparer{
-		{Name: "default", Compare: DefaultComparer.Compare, FormatKey: DefaultComparer.FormatKey},
 		{
-			Name:      "reverse",
-			Compare:   func(a, b []byte) int { return DefaultComparer.Compare(b, a) },
-			FormatKey: DefaultComparer.FormatKey,
+			Name:    "default",
+			Compare: DefaultComparer.Compare,
+		},
+		{
+			Name:    "reverse",
+			Compare: func(a, b []byte) int { return DefaultComparer.Compare(b, a) },
 		},
 	}
 	m := make(map[string]*Comparer)
 	for i := range comparers {
 		c := &comparers[i]
+		c.AbbreviatedKey = func(key []byte) uint64 { panic("unimplemented") }
+		c.Successor = func(dst, a []byte) []byte { panic("unimplemented") }
+		c.Separator = func(dst, a, b []byte) []byte { panic("unimplemented") }
 		m[c.Name] = c
 	}
 
diff --git a/internal/base/comparer.go b/internal/base/comparer.go
index bc5b1a3055..40628cb819 100644
--- a/internal/base/comparer.go
+++ b/internal/base/comparer.go
@@ -161,6 +161,9 @@ func (c *Comparer) EnsureDefaults() *Comparer {
 	if c == nil {
 		return DefaultComparer
 	}
+	if c.Compare == nil || c.AbbreviatedKey == nil || c.Separator == nil || c.Successor == nil || c.Name == "" {
+		panic("invalid Comparer: mandatory field not set")
+	}
 	if c.Equal != nil && c.FormatKey != nil {
 		return c
 	}
diff --git a/open_test.go b/open_test.go
index 569e17fe02..683bc5508c 100644
--- a/open_test.go
+++ b/open_test.go
@@ -348,8 +348,11 @@ func TestOpenOptionsCheck(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, d.Close())
 
+	fooCmp := *base.DefaultComparer
+	fooCmp.Name = "foo"
+
 	opts = &Options{
-		Comparer: &Comparer{Name: "foo"},
+		Comparer: &fooCmp,
 		FS:       mem,
 	}
 	_, err = Open("", opts)