diff --git a/src/arabic/ParadigmsAra.gf b/src/arabic/ParadigmsAra.gf
index 1be868289..f8531a2c2 100644
--- a/src/arabic/ParadigmsAra.gf
+++ b/src/arabic/ParadigmsAra.gf
@@ -201,36 +201,39 @@ resource ParadigmsAra = open
 
   mkV : overload {
     mkV : (imperfect : Str) -> V ; -- The verb in Per3 Sg Masc imperfect tense gives the most information
-    mkV : (root : Str) -> (perf,impf : Vowel) -> (masdar : Str) -> V ; -- verb form I ; vowel = a|i|u ; unpredictable masdar given as an argument.
-    mkV : (root : Str) -> (perf,impf : Vowel) -> V ; -- verb form I ; vowel = a|i|u ; dummy masdar inserted. This function is here only to keep compatibility for the old API; for new grammars, use the constructor with masdar as an argument.
-    mkV : (root : Str) -> VerbForm -> V ;  -- FormI .. FormX (no IX) ; default vowels a u for I, and dummy masdar. Forms II-X have predictable masdar.
+    mkV : (root : Str) -> (perf,impf : Vowel) -> (masdar : Str) -> V ; -- Verb form I. Vowel is one of {va,vi,vu}. Unpredictable masdar given as an argument.
+    mkV : (root : Str) -> (perf,impf : Vowel) -> V ; -- Like above, but dummy masdar inserted. This function is here only to keep compatibility for the old API; for new grammars, use the constructor with masdar as an argument.
+    mkV : (root,masdar : Str) -> VerbForm -> V ;  -- FormI…FormXI (no IX). XI is quadriliteral. For FormI, default vowels are va and vu, and dummy masdar is inserted. Forms II-XI have predictable masdar, so this constructor works fine.
+    mkV : (root : Str) -> VerbForm -> V ;  -- Like above, but dummy masdar inserted for FormI verbs. No difference for FormII-FormXI, because they have predictable masdar.
     mkV : V -> (particle : Str) -> V -- V with a non-inflecting particle/phrasal verb
     } ;
 
   reflV : V -> V ; -- نَفْس in the proper case and with possessive suffix, e.g.  نَفْسَكِ
 
   v1 = overload {
-    v1 : Str -> (perf,impf : Vowel) -> (masdar : Str) -> V -- Verb Form I : fa`ala, fa`ila, fa`ula. Verbal noun (masdar) given as the third argument.
+    v1 : (root : Str) -> (perf,impf : Vowel) -> (masdar : Str) -> V -- Verb Form I: fa`ala, fa`ila, fa`ula. Verbal noun (masdar) given as the third argument.
      = v1masdar ;
-    v1 : Str -> (perf,impf : Vowel) -> V -- To keep compatibility for the old API; dummy masdar inserted.
+    v1 : (root : Str) -> (perf,impf : Vowel) -> V -- To keep compatibility for the old API; dummy masdar inserted.
      = v1dummymasdar ;
   } ;
 
-  v2 : Str -> V ; -- Verb Form II : fa``ala
+  v2 : Str -> V ; -- Verb Form II: fa``ala
 
-  v3 : Str -> V ; -- Verb Form III : faa`ala
+  v3 : Str -> V ; -- Verb Form III: faa`ala
 
-  v4 : Str -> V ; -- Verb Form IV : 'af`ala
+  v4 : Str -> V ; -- Verb Form IV: 'af`ala
 
-  v5 : Str -> V ; -- Verb Form V : tafa``ala
+  v5 : Str -> V ; -- Verb Form V: tafa``ala
 
-  v6 : Str -> V ; -- Verb Form VI : tafaa`ala
+  v6 : Str -> V ; -- Verb Form VI: tafaa`ala
 
-  v7 : Str -> V ; -- Verb Form VII : infa`ala
+  v7 : Str -> V ; -- Verb Form VII: infa`ala
 
-  v8 : Str -> V ; -- Verb Form VIII ifta`ala
+  v8 : Str -> V ; -- Verb Form VIII: ifta`ala
 
-  v10 : Str -> V ; -- Verb Form X 'istaf`ala
+  v10 : Str -> V ; -- Verb Form X: 'istaf`ala
+
+  v11 : Str -> V ; -- Verb Form XI (quadriliteral): fa`laba
 
 --3 Two-place verbs
 
@@ -539,6 +542,17 @@ resource ParadigmsAra = open
           _               => v10sound fcl }
       } in lin V verb ;
 
+  v11 =
+    \rootStr ->
+    let fcl : Root3 = case rootStr of {
+          f@? + c@? + l@? + b@? => {f=f ; c=c+"ْ"+l ; l=b} ;
+          _ => Predef.error "v11: implement quadriliterals properly"
+        } ;
+        verb : Verb  = case rootStr of {
+          _ => v11sound fcl -- TODO more cases?
+        } ;
+    in lin V verb ;
+
   reflV v = lin V (ResAra.reflV v) ;
 
   mkFullN nsc gen spec = lin N
@@ -816,18 +830,19 @@ smartPN : Str -> PN = \s -> case last s of {
   } ;
 
 formV : (root : Str) -> VerbForm -> V = \s,f -> case f of {
-   FormI   => v1 s a u ;
-   FormII  => v2 s ;
-   FormIII => v3 s ;
-   FormIV  => v4 s ;
-   FormV   => v5 s ;
-   FormVI  => v6 s ;
+   FormI    => v1 s a u ;
+   FormII   => v2 s ;
+   FormIII  => v3 s ;
+   FormIV   => v4 s ;
+   FormV    => v5 s ;
+   FormVI   => v6 s ;
    FormVII  => v7 s ;
    FormVIII => v8 s ;
-   FormX   => v10 s
+   FormX    => v10 s ;
+   FormXI   => v11 s
    } ;
 
 param VerbForm =
-  FormI | FormII | FormIII | FormIV | FormV | FormVI | FormVII | FormVIII | FormX ;
+  FormI | FormII | FormIII | FormIV | FormV | FormVI | FormVII | FormVIII | FormX | FormXI ;
 
 } ;
diff --git a/src/arabic/ResAra.gf b/src/arabic/ResAra.gf
index b95b3c5af..611ea91ff 100644
--- a/src/arabic/ResAra.gf
+++ b/src/arabic/ResAra.gf
@@ -41,7 +41,6 @@ resource ResAra = PatternsAra ** open  Prelude, Predef, OrthoAra, ParamX  in {
     Root2   : Type = Root ** {c : Str} ;
     Root3   : Type = Root2 ** {l : Str} ;
 
--- AR 7/12/2009 changed this to avoid duplication of consonants
     mkRoot3 : Str -> Root3 = \fcl -> case fcl of {
       f@? + c@? + l => {f = f ; c = c ; l = l} ;
       _ => error ("mkRoot3: too short root" ++ fcl)
@@ -237,13 +236,13 @@ oper
         })
     } ;
   verb' : SoundForms -> Verb = \vforms ->
-   let katab = vforms ! 0 ;
-       kutib = vforms ! 1 ;
-       aktub = vforms ! 2 ;
-       uktab = vforms ! 3 ;
-       euktub = vforms ! 4 ;
-       maktUb = vforms ! 5 ;
-       katb   = vforms ! 6 ;
+   let katab = vforms ! 0 ; -- VPerf Act
+       kutib = vforms ! 1 ; -- VPerf Pas
+       aktub = vforms ! 2 ; -- VImpf _ Act
+       uktab = vforms ! 3 ; -- VImpf _ Pas
+       euktub = vforms ! 4 ; -- VImp
+       maktUb = vforms ! 5 ; -- VPPart
+       katb   = vforms ! 6 ; -- Masdar
     in verb katab kutib aktub uktab euktub maktUb katb ;
   --affixes of sound verbs
 
@@ -1042,6 +1041,18 @@ v10geminate : Str -> Verb = \fcl ->
          n@(6|7) => "ُسْتَ" + vforms ! n -- ???
     }) ;
 
+v11sound : Root3 -> Verb = \fclb ->
+  let faclabat = mkStrong facalp fclb ;
+      faclib = mkStrong facil fclb ;
+      faclab = mkStrong facal fclb ;
+      vforms = table {
+        2 => "ُ" + faclib ; -- VImpf Act
+        3 => "ُ" + faclab ; -- VImpf Pas
+        5 => "مُ" + faclab ; -- VPPart
+        n => v1soundForms fclb a i faclabat ! n
+      } ;
+   in verb' vforms ;
+
 patV1Perf : Vowel => Pattern =
   table {
     a => facal ; --katab