diff --git a/Text/Inflections/Types.hs b/Text/Inflections/Types.hs
index 33b82c2..06b42f5 100644
--- a/Text/Inflections/Types.hs
+++ b/Text/Inflections/Types.hs
@@ -31,7 +31,7 @@ module Text.Inflections.Types
 where
 
 import Control.Monad.Catch
-import Data.Char (isSpace)
+import Data.Char (isAlphaNum)
 import Data.Data (Data)
 import Data.Text (Text)
 import Data.Typeable (Typeable)
@@ -43,28 +43,30 @@ import qualified Data.Text as T
 import Prelude hiding (Word)
 #endif
 
--- | Create a word from given 'Text'. The input should not contain spaces or
+-- | Create a word from given 'Text'. The input should consist of only
+-- alpha-numeric characters (no white spaces or punctuation)
 -- 'InflectionInvalidWord' will be thrown.
 --
 -- /since 0.3.0.0/
 
 mkWord :: MonadThrow m => Text -> m (Word 'Normal)
 mkWord txt =
-  if T.any isSpace txt
-    then throwM (InflectionInvalidWord txt)
-    else return (Word txt)
+  if T.all isAlphaNum txt
+    then return (Word txt)
+    else throwM (InflectionInvalidWord txt)
 
--- | Create an acronym from given 'Text'. The input should not contain
--- spaces or 'InflectionInvalidAcronym' will be thrown. Acronym is different
--- from normal word by that it may not be transformed by inflections.
+-- | Create an acronym from given 'Text'. The input should consist of only
+-- alpha-numeric characters 'InflectionInvalidAcronym' will be thrown.
+-- Acronym is different from normal word by that it may not be transformed
+-- by inflections (also see 'unSomeWord').
 --
 -- /since 0.3.0.0/
 
 mkAcronym :: MonadThrow m => Text -> m (Word 'Acronym)
 mkAcronym txt =
-  if T.any isSpace txt
-    then throwM (InflectionInvalidAcronym txt)
-    else return (Word txt)
+  if T.all isAlphaNum txt
+    then return (Word txt)
+    else throwM (InflectionInvalidAcronym txt)
 
 -- | A 'Text' value that should be kept whole through applied inflections.
 
diff --git a/inflections.cabal b/inflections.cabal
index 12ce9ef..03b4bbb 100644
--- a/inflections.cabal
+++ b/inflections.cabal
@@ -78,5 +78,6 @@ test-suite test
                      , Text.Inflections.Parse.SnakeCaseSpec
                      , Text.Inflections.TitleizeSpec
                      , Text.Inflections.TransliterateSpec
+                     , Text.Inflections.TypesSpec
                      , Text.Inflections.UnderscoreSpec
                      , Text.InflectionsSpec
diff --git a/test/Text/Inflections/HumanizeSpec.hs b/test/Text/Inflections/HumanizeSpec.hs
index a31ece5..ed013c4 100644
--- a/test/Text/Inflections/HumanizeSpec.hs
+++ b/test/Text/Inflections/HumanizeSpec.hs
@@ -19,8 +19,9 @@ spec = describe "humazine" $ do
     humanize [employee,salary] `shouldBe` "Employee salary"
   it "turns underscores into spaces" $ do
     employee  <- SomeWord <$> mkWord "employee"
-    hasSalary <- SomeWord <$> mkWord "has_salary"
-    humanize [employee, hasSalary] `shouldBe` "Employee has salary"
+    has       <- SomeWord <$> mkWord "has"
+    salary    <- SomeWord <$> mkWord "salary"
+    humanize [employee, has, salary] `shouldBe` "Employee has salary"
   it "capitalizes the first word of a sentence" $ do
     underground <- SomeWord <$> mkWord "underground"
     humanize [underground] `shouldBe` "Underground"
diff --git a/test/Text/Inflections/TypesSpec.hs b/test/Text/Inflections/TypesSpec.hs
new file mode 100644
index 0000000..e0b7205
--- /dev/null
+++ b/test/Text/Inflections/TypesSpec.hs
@@ -0,0 +1,51 @@
+{-# LANGUAGE CPP               #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Text.Inflections.TypesSpec
+  ( spec )
+where
+
+import Test.Hspec
+import Text.Inflections
+import qualified Data.Text as T
+
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative
+#endif
+
+spec :: Spec
+spec = do
+  describe "mkWord" $ do
+    context "when provided a correct Text value" $
+      it "creates a normal word" $ do
+        x <- mkWord "foo"
+        unWord x `shouldBe` "foo"
+    context "when provided an incorrect Text value" $
+      it "throws the correct exception" $ do
+        mkWord "foo bar" `shouldThrow` (== InflectionInvalidWord "foo bar")
+        mkWord "foo_" `shouldThrow` (== InflectionInvalidWord "foo_")
+        mkWord "&$?%" `shouldThrow` (== InflectionInvalidWord "&$?%")
+  describe "mkAcronym" $ do
+    context "when provided a correct Text value" $
+      it "creates an acronym" $ do
+        x <- mkAcronym "foo"
+        unWord x `shouldBe` "foo"
+    context "when providde an incorrect Text value" $
+      it "throws the correct exception" $ do
+        mkAcronym "foo bar" `shouldThrow` (== InflectionInvalidAcronym "foo bar")
+        mkAcronym "foo_" `shouldThrow` (== InflectionInvalidAcronym "foo_")
+        mkAcronym "&$?%" `shouldThrow` (== InflectionInvalidAcronym "&$?%")
+  describe "unWord" $
+    it "extracts the inner Text value" $ do
+      (unWord <$> mkWord "foo")    `shouldReturn` "foo"
+      (unWord <$> mkWord "bar")    `shouldReturn` "bar"
+      (unWord <$> mkAcronym "baz") `shouldReturn` "baz"
+  describe "unSomeWord" $ do
+    context "when inner value is a normal word" $
+      it "Text is extracted and the given function applied" $ do
+        x <- SomeWord <$> mkWord "word"
+        unSomeWord T.toUpper x `shouldBe` "WORD"
+    context "when inner value is an acronym" $
+      it "Text is extracted, but the function is not applied" $ do
+        x <- SomeWord <$> mkAcronym "acronym"
+        unSomeWord T.toUpper x `shouldBe` "acronym"