diff --git a/custom_data.go b/custom_data.go
index 9a2dfc7..efb445f 100644
--- a/custom_data.go
+++ b/custom_data.go
@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 func init() {
@@ -75,6 +76,10 @@ func LoadInflections(r io.Reader) error {
 	defer singularMoot.Unlock()
 
 	for s, p := range m {
+		if strings.Contains(s, " ") || strings.Contains(p, " ") {
+			// flect works with parts, so multi-words should not be allowed
+			return fmt.Errorf("inflection elements should be a single word")
+		}
 		singleToPlural[s] = p
 		pluralToSingle[p] = s
 	}
diff --git a/flect_test.go b/flect_test.go
index d6b92e8..59782bc 100644
--- a/flect_test.go
+++ b/flect_test.go
@@ -16,8 +16,8 @@ type tt struct {
 func Test_LoadInflections(t *testing.T) {
 	r := require.New(t)
 	m := map[string]string{
-		"beatle": "the beatles",
-		"xyz":    "zyx",
+		"baby": "bebe",
+		"xyz":  "zyx",
 	}
 
 	b, err := json.Marshal(m)
@@ -33,6 +33,30 @@ func Test_LoadInflections(t *testing.T) {
 	}
 }
 
+func Test_LoadInflectionsWrongSingular(t *testing.T) {
+	r := require.New(t)
+	m := map[string]string{
+		"a file": "files",
+	}
+
+	b, err := json.Marshal(m)
+	r.NoError(err)
+
+	r.Error(LoadInflections(bytes.NewReader(b)))
+}
+
+func Test_LoadInflectionsWrongPlural(t *testing.T) {
+	r := require.New(t)
+	m := map[string]string{
+		"beatle": "the beatles",
+	}
+
+	b, err := json.Marshal(m)
+	r.NoError(err)
+
+	r.Error(LoadInflections(bytes.NewReader(b)))
+}
+
 func Test_LoadAcronyms(t *testing.T) {
 	r := require.New(t)
 	m := []string{
@@ -53,6 +77,16 @@ func Test_LoadAcronyms(t *testing.T) {
 
 var singlePluralAssertions = []tt{
 	{"", ""},
+	{"Car", "Cars"},
+	{"Boy", "Boys"},
+	{"GoodBoy", "GoodBoys"},
+	{"Axis", "Axes"},
+	{"Child", "Children"},
+	{"GoodChild", "GoodChildren"},
+	{"SmartPerson", "SmartPeople"},
+	{"SuperbOx", "SuperbOxen"},
+	{"WildOx", "WildOxen"},
+	{"wild_ox", "wild_oxen"},
 	{"ability", "abilities"},
 	{"address", "addresses"},
 	{"agency", "agencies"},
@@ -76,6 +110,7 @@ var singlePluralAssertions = []tt{
 	{"child", "children"},
 	{"circus", "circuses"},
 	{"city", "cities"},
+	{"collapse", "collapses"},
 	{"comment", "comments"},
 	{"crisis", "crises"},
 	{"criterion", "criteria"},
@@ -89,6 +124,7 @@ var singlePluralAssertions = []tt{
 	{"diagnosis_a", "diagnosis_as"},
 	{"diagnosis", "diagnoses"},
 	{"dwarf", "dwarves"},
+	{"eclipse", "eclipses"},
 	{"edge", "edges"},
 	{"elf", "elves"},
 	{"ellipsis", "ellipses"},
@@ -105,6 +141,7 @@ var singlePluralAssertions = []tt{
 	{"fox", "foxes"},
 	{"funky jeans", "funky jeans"},
 	{"fuse", "fuses"},
+	{"glimpse", "glimpses"},
 	{"goose", "geese"},
 	{"great_person", "great_people"},
 	{"half", "halves"},
@@ -115,11 +152,13 @@ var singlePluralAssertions = []tt{
 	{"index", "indices"},
 	{"information", "information"},
 	{"jeans", "jeans"},
+	{"lapse", "lapses"},
 	{"louse", "lice"},
 	{"lunch", "lunches"},
 	{"marsh", "marshes"},
 	{"matrix", "matrices"},
-	{"media", "media"},
+	{"medium", "media"},
+	{"multimedia", "multimedia"},
 	{"mouse", "mice"},
 	{"move", "moves"},
 	{"movie", "movies"},
@@ -130,6 +169,7 @@ var singlePluralAssertions = []tt{
 	{"ovum", "ova"},
 	{"ox", "oxen"},
 	{"payment_information", "payment_information"},
+	{"pepsi", "pepsis"},
 	{"person", "people"},
 	{"perspective", "perspectives"},
 	{"phenomenon", "phenomena"},
@@ -141,6 +181,7 @@ var singlePluralAssertions = []tt{
 	{"prize", "prizes"},
 	{"process", "processes"},
 	{"prometheus", "prometheuses"},
+	{"psi", "psis"},
 	{"puppy", "puppies"},
 	{"query", "queries"},
 	{"quiz", "quizzes"},
@@ -170,6 +211,7 @@ var singlePluralAssertions = []tt{
 	{"tooth", "teeth"},
 	{"truss", "trusses"},
 	{"user", "users"},
+	{"user_custom_field", "user_custom_fields"},
 	{"vedalia", "vedalias"},
 	{"virus", "viri"},
 	{"wife", "wives"},
diff --git a/go.mod b/go.mod
index 83d2244..64ce253 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module github.com/gobuffalo/flect
 
 go 1.16
 
-require github.com/stretchr/testify v1.7.1
+require github.com/stretchr/testify v1.8.0
diff --git a/go.sum b/go.sum
index 2dca7c9..5164829 100644
--- a/go.sum
+++ b/go.sum
@@ -1,11 +1,15 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/plural_rules.go b/plural_rules.go
index 61d34d3..7205ec0 100644
--- a/plural_rules.go
+++ b/plural_rules.go
@@ -47,6 +47,7 @@ var singleToPlural = map[string]string{
 	"concerto":    "concertos",
 	"corpus":      "corpora",
 	"crisis":      "crises",
+	"criterion":   "criteria",
 	"curriculum":  "curriculums",
 	"datum":       "data",
 	"deer":        "deer",
@@ -56,7 +57,6 @@ var singleToPlural = map[string]string{
 	"ellipsis":    "ellipses",
 	"equipment":   "equipment",
 	"erratum":     "errata",
-	"faux pas":    "faux pas",
 	"fez":         "fezzes",
 	"fish":        "fish",
 	"focus":       "foci",
@@ -82,6 +82,7 @@ var singleToPlural = map[string]string{
 	"locus":       "loci",
 	"louse":       "lice",
 	"matrix":      "matrices",
+	"medium":      "media",
 	"minutia":     "minutiae",
 	"money":       "money",
 	"moose":       "moose",
@@ -96,6 +97,7 @@ var singleToPlural = map[string]string{
 	"ovum":        "ova",
 	"ox":          "oxen",
 	"parenthesis": "parentheses",
+	"person":      "people",
 	"phenomenon":  "phenomena",
 	"photo":       "photos",
 	"phylum":      "phyla",
@@ -157,9 +159,7 @@ type singularToPluralSuffix struct {
 }
 
 var singularToPluralSuffixList = []singularToPluralSuffix{
-	{"iterion", "iteria"},
 	{"campus", "campuses"},
-	{"genera", "genus"},
 	{"person", "people"},
 	{"phylum", "phyla"},
 	{"randum", "randa"},
@@ -169,6 +169,7 @@ var singularToPluralSuffixList = []singularToPluralSuffix{
 	{"child", "children"},
 	{"chive", "chives"},
 	{"focus", "foci"},
+	{"genus", "genera"},
 	{"hello", "hellos"},
 	{"jeans", "jeans"},
 	{"louse", "lice"},
@@ -195,7 +196,6 @@ var singularToPluralSuffixList = []singularToPluralSuffix{
 	{"oose", "eese"},
 	{"ouse", "ouses"},
 	{"ovum", "ova"},
-	{"rion", "ria"},
 	{"shoe", "shoes"},
 	{"stis", "stes"},
 	{"tive", "tives"},
@@ -225,7 +225,6 @@ var singularToPluralSuffixList = []singularToPluralSuffix{
 	{"ode", "odes"},
 	{"ofe", "oves"},
 	{"pfe", "pves"},
-	{"pse", "psis"},
 	{"qfe", "qves"},
 	{"quy", "quies"},
 	{"rfe", "rves"},
diff --git a/pluralize.go b/pluralize.go
index e265f84..88f9ec5 100644
--- a/pluralize.go
+++ b/pluralize.go
@@ -43,6 +43,9 @@ func (i Ident) Pluralize() Ident {
 		return i
 	}
 	if p, ok := singleToPlural[ls]; ok {
+		if s == Capitalize(s) {
+			p = Capitalize(p)
+		}
 		return i.ReplaceSuffix(s, p)
 	}
 	for _, r := range pluralRules {
diff --git a/singularize.go b/singularize.go
index 1ed4995..244e382 100644
--- a/singularize.go
+++ b/singularize.go
@@ -30,28 +30,32 @@ func SingularizeWithSize(s string, i int) string {
 //	data = datum
 //	people = person
 func (i Ident) Singularize() Ident {
-	s := i.Original
+	s := i.LastPart()
 	if len(s) == 0 {
 		return i
 	}
 
 	singularMoot.RLock()
 	defer singularMoot.RUnlock()
+
 	ls := strings.ToLower(s)
 	if p, ok := pluralToSingle[ls]; ok {
-		return New(p)
+		if s == Capitalize(s) {
+			p = Capitalize(p)
+		}
+		return i.ReplaceSuffix(s, p)
 	}
 	if _, ok := singleToPlural[ls]; ok {
 		return i
 	}
 	for _, r := range singularRules {
 		if strings.HasSuffix(ls, r.suffix) {
-			return New(r.fn(s))
+			return i.ReplaceSuffix(s, r.fn(s))
 		}
 	}
 
 	if strings.HasSuffix(s, "s") {
-		return New(s[:len(s)-1])
+		return i.ReplaceSuffix("s", "")
 	}
 	return i
 }