diff --git a/CloogleServer.icl b/CloogleServer.icl
index cf16a0cd9360b93538d08a311aa205585e73868d..cd4311567251e3854f42e96591a7e9997fe20300 100644
--- a/CloogleServer.icl
+++ b/CloogleServer.icl
@@ -104,6 +104,7 @@ err c m = { return         = c
 E_NORESULTS :== 127
 E_INVALIDINPUT :== 128
 E_NAMETOOLONG :== 129
+E_INVALIDTYPE :== 130
 
 MAX_RESULTS :== 15
 
@@ -129,6 +130,8 @@ where
 	handle db (Just request=:{unify,name,modules,page}) w
 		| isJust name && size (fromJust name) > 40
 			= (err E_NAMETOOLONG "function name too long", w)
+		| isJust unify && isNothing (parseType $ fromString $ fromJust unify)
+			= (err E_INVALIDTYPE "couldn't parse type", w)
 		// Results
 		# drop_n = fromJust (page <|> pure 0) * MAX_RESULTS
 		# results = drop drop_n $ sort $ search request db
diff --git a/README.md b/README.md
index 4763d08b45c335a2749d51add41e9414b45e0c30..d57508482c1134d12bf662eba1f7ce3de2461c61 100644
--- a/README.md
+++ b/README.md
@@ -61,6 +61,7 @@ fields:
 	* `127`: no results
 	* `128`: ununderstandable input (usually shouldn't happen)
 	* `129`: function name too long
+	* `130`: couldn't parse type
 	* `150`: the Clean backend could not be reached
 	* `151`: invalid request type (should use GET)
 	* `152`: no input (GET variable `str` should be set to the search string)