diff --git a/.github/workflows/src.yml b/.github/workflows/src.yml
index 8d6bedf..0c0e228 100644
--- a/.github/workflows/src.yml
+++ b/.github/workflows/src.yml
@@ -7,9 +7,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: aviate-labs/setup-dfx@v0.2.2
+      - uses: aviate-labs/setup-dfx@v0.2.3
         with:
-          dfx-version: 0.8.0
-          install-moc: true
+          dfx-version: 0.8.4
           vessel-version: 0.6.2
-      - run: for i in src/*.mo ; do moc $(vessel sources) --check $i ; done
+      - run: for i in src/*.mo ; do $(vessel bin)/moc $(vessel sources) --check $i ; done
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index cfc02cd..bec6d0f 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -7,9 +7,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-      - uses: aviate-labs/setup-dfx@v0.2.2
+      - uses: aviate-labs/setup-dfx@v0.2.3
         with:
-          dfx-version: 0.8.0
-          install-moc: true
+          dfx-version: 0.8.4
           vessel-version: 0.6.2
-      - run: for i in test/*.mo ; do moc $(vessel sources) -r $i ; done
+      - run: for i in test/*.mo ; do $(vessel bin)/moc $(vessel sources) -r $i ; done
diff --git a/src/XorShift.mo b/src/XorShift.mo
index 5946a27..7d5b901 100644
--- a/src/XorShift.mo
+++ b/src/XorShift.mo
@@ -25,7 +25,7 @@ module {
             state ^= (state >> 12);
             state ^= (state << 25);
             state ^= (state >> 27);
-            state * 2685821657736338717;
+            state *% 2685821657736338717;
         };
     };
 
diff --git a/test/XorShift.mo b/test/XorShift.mo
new file mode 100644
index 0000000..1360b01
--- /dev/null
+++ b/test/XorShift.mo
@@ -0,0 +1,19 @@
+import Hash "mo:base/Hash";
+import Nat "mo:base/Nat";
+import Nat64 "mo:base/Nat64";
+import Text "mo:base/Text";
+import TrieSet "mo:base/TrieSet";
+
+import XorShift "../src/XorShift";
+
+import Debug "mo:base/Debug";
+
+var r = XorShift.XorShift64(null);
+var s = TrieSet.empty<Text>();
+var i = 0;
+while (i < 99) {
+    let n = Nat64.toText(r.next());
+    s := TrieSet.put<Text>(s, n, Text.hash(n), Text.equal);
+    i += 1;
+};
+assert(TrieSet.size(s) == 99);