diff --git a/src/ltlast/binop.cc b/src/ltlast/binop.cc
index 04b87fd37..0fa9fbf23 100644
--- a/src/ltlast/binop.cc
+++ b/src/ltlast/binop.cc
@@ -49,12 +49,16 @@ namespace spot
       // universality and eventuality.
       props = first->get_props() & second->get_props();
       // The matter can be further refined because:
-      //  (f U g) and (g M f) are pure eventualities if
-      //                         g is a pure eventuality (regardless of f)
-      //                      or f == 1
-      //  (f W g) and (g R f) are purely universal if
-      //                         f is purely universal (regardless of g)
-      //                      or g == 0
+      //  (f U g) is a pure eventuality if
+      //                g is a pure eventuality (regardless of f),
+      //             or f == 1
+      //  (g M f) is a pure eventuality if f and g are,
+      //                                or f == 1
+      //  (g R f) is purely universal if
+      //                f is purely universal (regardless of g)
+      //               or g == 0
+      //  (f W g) is purely universal if f and g are
+      //                              or g == 0
       switch (op)
 	{
 	case Xor:
@@ -177,8 +181,7 @@ namespace spot
 	  // is.syntactic_persistence = Persistence U Persistance
 	  break;
 	case W:
-	  // f W g is universal if f is universal, or if g == 0.
-	  is.universal = first->is_universal();
+	  // f W g is universal if f and g are, or if g == 0.
 	  is.universal |= (second == constant::false_instance());
 	  is.boolean = false;
 	  is.eltl_formula = false;
@@ -217,8 +220,7 @@ namespace spot
 
 	  break;
 	case M:
-	  // g M f is universal if g is eventual, or if f == 1.
-	  is.eventual = first->is_eventual();
+	  // g M f is eventual if both g and f are eventual, or if f == 1.
 	  is.eventual |= (second == constant::true_instance());
 	  is.boolean = false;
 	  is.eltl_formula = false;
diff --git a/src/ltltest/kind.test b/src/ltltest/kind.test
index 4ea1d9af2..1211033e0 100755
--- a/src/ltltest/kind.test
+++ b/src/ltltest/kind.test
@@ -104,6 +104,8 @@ check 'Fa  M GFb' '&!xLPer'
 check 'GFa W GFb' '&!xLPeur'
 check 'FGa W FGb' '&!xLPeu'
 check 'Ga  W FGb' '&!xLPup'
+check 'Ga  W b'   '&!xLPsopr'
+check 'Fa  M b'   '&!xLPgopr'
 check '{a;b*;c}' '&!xfPsopr'
 check '{a;b*;c}!' '&!xfPgopr'
 check '!{a;b*;c}!' '&xfPsopr'  # The negative normal form is {a;b*;c}[]->0