diff --git a/src/Network/GemServ.hs b/src/Network/GemServ.hs
index 6f9946d..9ab6455 100644
--- a/src/Network/GemServ.hs
+++ b/src/Network/GemServ.hs
@@ -25,9 +25,11 @@ License along with this program.  If not, see
 -}
 
 module Network.GemServ (
-  encodeRequest
+  encodeRequest,
+  escapeString
 ) where
 
+import Data.Char (ord)
 import Data.List (intercalate)
 
 import Network.GemServ.Types
@@ -45,4 +47,21 @@ encodeRequest req =
       "" -> ""
       q  -> '?' : q
 
+-- | add required escape sequences to a string
+escapeString :: String -> String
+escapeString = concatMap $ \ch ->
+  if ch `elem` unescaped
+  then [ch]
+  else '%' : toHex ch
+  where
+    unescaped = ['0'..'9'] ++ ['A'..'Z'] ++ ['a'..'z'] ++ "~-_."
+    toHex ch  = let
+      n    = ord ch
+      high = n `div` 16
+      low  = n `mod` 16
+      in [hexDigits !! high, hexDigits !! low]
+
+hexDigits :: String
+hexDigits = ['0'..'9'] ++ ['a'..'f']
+
 --jl
diff --git a/test/Network/GemServSpec.hs b/test/Network/GemServSpec.hs
index 4cde415..7657075 100644
--- a/test/Network/GemServSpec.hs
+++ b/test/Network/GemServSpec.hs
@@ -28,8 +28,9 @@ import Network.GemServ
 import Network.GemServ.Types
 
 spec :: Spec
-spec = describe "Network.GemServ"
+spec = describe "Network.GemServ" $ do
   encodeRequestSpec
+  escapeStringSpec
 
 encodeRequestSpec :: Spec
 encodeRequestSpec = describe "encodeRequest" $ mapM_
@@ -55,4 +56,16 @@ encodeRequestSpec = describe "encodeRequest" $ mapM_
     withQueryReq = simpleReq { reqQuery = "foo" }
     withQueryExp = "gemini://example.com/?foo"
 
+escapeStringSpec :: Spec
+escapeStringSpec = describe "escapeString" $ mapM_
+  ( \(input, expected) -> context (show input) $
+    it ("should be " ++ show expected) $
+      escapeString input `shouldBe` expected
+  )
+
+  --  input,               expected
+  [ ( "~foo-bar_baz.quux", "~foo-bar_baz.quux"        )
+  , ( "foo:/?=&#%",        "foo%3a%2f%3f%3d%26%23%25" )
+  ]
+
 --jl