diff --git a/src/Common.elm b/src/Common.elm
index 141f10d..a085bc3 100644
--- a/src/Common.elm
+++ b/src/Common.elm
@@ -276,7 +276,7 @@ replaceSymbolsWith replacement input =
     input
         |> String.map
             (\c ->
-                if c /= '_' && not (Char.isAlphaNum c) then
+                if Char.toCode c /= {- '_' -} 95 && not (Char.isAlphaNum c) then
                     replacement
 
                 else
diff --git a/src/OpenApi/Generate.elm b/src/OpenApi/Generate.elm
index c3e7029..0d415a7 100644
--- a/src/OpenApi/Generate.elm
+++ b/src/OpenApi/Generate.elm
@@ -2734,7 +2734,7 @@ makeNamespaceValid : String -> String
 makeNamespaceValid str =
     String.map
         (\char ->
-            if List.member char invalidModuleNameChars then
+            if isInvalidForModuleName char then
                 '_'
 
             else
@@ -2745,18 +2745,22 @@ makeNamespaceValid str =
 
 removeInvalidChars : String -> String
 removeInvalidChars str =
-    String.filter (\char -> char /= '\'') str
-
-
-invalidModuleNameChars : List Char
-invalidModuleNameChars =
-    [ ' '
-    , '.'
-    , '/'
-    , '{'
-    , '}'
-    , '-'
-    , ':'
-    , '('
-    , ')'
-    ]
+    String.filter (\char -> Char.toCode char /= {- '\'' -} 39) str
+
+
+isInvalidForModuleName : Char -> Bool
+isInvalidForModuleName char =
+    let
+        code : Int
+        code =
+            Char.toCode char
+    in
+    (code == {- ' ' -} 32)
+        || (code == {- '.' -} 46)
+        || (code == {- '/' -} 47)
+        || (code == {- '{' -} 123)
+        || (code == {- '}' -} 125)
+        || (code == {- '-' -} 45)
+        || (code == {- ':' -} 58)
+        || (code == {- '(' -} 40)
+        || (code == {- ')' -} 41)
diff --git a/src/Utils.elm b/src/Utils.elm
index e81974a..0237d85 100644
--- a/src/Utils.elm
+++ b/src/Utils.elm
@@ -12,10 +12,16 @@ sanitizeModuleName str =
             String.filter
                 (\char ->
                     Char.isAlphaNum char
-                        || (char == '_')
-                        || (char == '-')
-                        || (char == ' ')
-                        || (char == ':')
+                        || (let
+                                code : Int
+                                code =
+                                    Char.toCode char
+                            in
+                            (code == {- '_' -} 95)
+                                || (code == {- '-' -} 45)
+                                || (code == {- ' ' -} 32)
+                                || (code == {- ':' -} 58)
+                           )
                 )
                 str
                 |> String.replace "_" " "
diff --git a/tests/TestCommon.elm b/tests/TestCommon.elm
index 0b9f710..b82e994 100644
--- a/tests/TestCommon.elm
+++ b/tests/TestCommon.elm
@@ -179,7 +179,7 @@ isLower c =
 
 isAlphaNumOrUnderscore : Char -> Bool
 isAlphaNumOrUnderscore c =
-    Char.isAlphaNum c || c == '_' || Unicode.isAlphaNum c
+    Char.isAlphaNum c || Char.toCode c == {- '_' -} 95 || Unicode.isAlphaNum c
 
 
 escape : String -> String