diff --git a/src/hash.cc b/src/hash.cc
index 342e37a7..058985b3 100644
--- a/src/hash.cc
+++ b/src/hash.cc
@@ -3,6 +3,9 @@
 #include <cstdint>
 #include <cstring>
 
+#include "unit_tests.hh"
+#include "assert.hh"
+
 namespace Kakoune
 {
 
@@ -50,10 +53,12 @@ size_t hash_data(const char* input, size_t len)
 
     const uint8_t* tail = data + nblocks * 4;
     uint32_t key = 0;
-    switch (len & 3)
+    switch (len & 0b11)
     {
-        case 3: key ^= tail[2] << 16; /* fallthrough */
-        case 2: key ^= tail[1] << 8;  /* fallthrough */
+        case 3: key ^= tail[2] << 16;
+            [[fallthrough]];
+        case 2: key ^= tail[1] << 8;
+            [[fallthrough]];
         case 1: key ^= tail[0];
                 key *= c1;
                 key = rotl(key,15);
@@ -67,4 +72,16 @@ size_t hash_data(const char* input, size_t len)
     return hash;
 }
 
+UnitTest test_murmer_hash{[] {
+    {
+        constexpr char data[] = "Hello, World!";
+        kak_assert(hash_data(data, strlen(data)) == 0xf816f95b);
+    }
+    {
+        constexpr char data[] = "xxxxxxxxxxxxxxxxxxxxxxxxxxxx";
+        kak_assert(hash_data(data, strlen(data)) == 3551113186);
+    }
+    kak_assert(hash_data("", 0) == 2572747774);
+}};
+
 }