diff --git a/lib/linguist/samples.json b/lib/linguist/samples.json
index aa13d4b2..d9c1559a 100644
--- a/lib/linguist/samples.json
+++ b/lib/linguist/samples.json
@@ -851,8 +851,8 @@
       "exception.zep.php"
     ]
   },
-  "tokens_total": 654836,
-  "languages_total": 903,
+  "tokens_total": 654867,
+  "languages_total": 904,
   "tokens": {
     "ABAP": {
       "*/**": 1,
@@ -55996,9 +55996,19 @@
       "TWO_PI": 1
     },
     "Prolog": {
-      "-": 161,
+      "%": 72,
+      "subset": 2,
+      "(": 332,
+      "Set": 4,
+      "Subset": 6,
+      ")": 331,
+      "-": 163,
+      "append": 3,
+      "L1": 1,
+      ".": 109,
+      "powerset": 1,
+      "bagof": 1,
       "module": 3,
-      "(": 327,
       "format_spec": 12,
       "[": 87,
       "format_error/2": 1,
@@ -56007,8 +56017,6 @@
       "spec_arity/2": 1,
       "spec_types/2": 1,
       "]": 87,
-      ")": 326,
-      ".": 107,
       "use_module": 8,
       "library": 8,
       "dcg/basics": 1,
@@ -56018,7 +56026,6 @@
       "error": 6,
       "when": 3,
       "when/2": 1,
-      "%": 71,
       "mavis": 1,
       "format_error": 8,
       "+": 14,
@@ -56291,7 +56298,6 @@
       "Goals": 2,
       "Tmp": 3,
       "instantiation_error": 1,
-      "append": 2,
       "NewArgs": 2,
       "variant_sha1": 1,
       "Sha": 2,
@@ -72845,7 +72851,7 @@
     "PostScript": 107,
     "PowerShell": 12,
     "Processing": 74,
-    "Prolog": 2420,
+    "Prolog": 2451,
     "Propeller Spin": 13519,
     "Protocol Buffer": 63,
     "PureScript": 1652,
@@ -73060,7 +73066,7 @@
     "PostScript": 1,
     "PowerShell": 2,
     "Processing": 1,
-    "Prolog": 5,
+    "Prolog": 6,
     "Propeller Spin": 10,
     "Protocol Buffer": 1,
     "PureScript": 4,
@@ -73127,5 +73133,5 @@
     "fish": 3,
     "wisp": 1
   },
-  "md5": "74f6109f5d8edac6b3f2bd3d65b9d210"
+  "md5": "a27211466edff986df556defef2e4e84"
 }
\ No newline at end of file
diff --git a/samples/Prolog/ex6.pl b/samples/Prolog/ex6.pl
new file mode 100644
index 00000000..0b1b74eb
--- /dev/null
+++ b/samples/Prolog/ex6.pl
@@ -0,0 +1,5 @@
+%6.8
+subset(Set, Subset) :-
+	append(L1, Subset, Set).
+powerset(Set, Subset) :-
+	bagof(Subset, subset(Set, Subset), Subset).