--- a/Python/pyhash.c	2017-11-29 10:21:20.283094068 +0100
+++ a/Python/pyhash.c	2017-11-29 10:24:26.733087813 +0100
@@ -372,7 +372,7 @@ siphash24(const void *src, Py_ssize_t sr
     PY_UINT64_T k0 = _le64toh(_Py_HashSecret.siphash.k0);
     PY_UINT64_T k1 = _le64toh(_Py_HashSecret.siphash.k1);
     PY_UINT64_T b = (PY_UINT64_T)src_sz << 56;
-    const PY_UINT64_T *in = (PY_UINT64_T*)src;
+    const PY_UINT8_T *in = (PY_UINT8_T*)src;
 
     PY_UINT64_T v0 = k0 ^ 0x736f6d6570736575ULL;
     PY_UINT64_T v1 = k1 ^ 0x646f72616e646f6dULL;
@@ -381,12 +381,14 @@ siphash24(const void *src, Py_ssize_t sr
 
     PY_UINT64_T t;
     PY_UINT8_T *pt;
-    PY_UINT8_T *m;
+    const PY_UINT8_T *m;
 
     while (src_sz >= 8) {
-        PY_UINT64_T mi = _le64toh(*in);
-        in += 1;
-        src_sz -= 8;
+        PY_UINT64_T mi;
+        memcpy(&mi, in, sizeof(mi));
+        mi = _le64toh(mi);
+        in += sizeof(mi);
+        src_sz -= sizeof(mi);
         v3 ^= mi;
         DOUBLE_ROUND(v0,v1,v2,v3);
         v0 ^= mi;
@@ -394,7 +396,7 @@ siphash24(const void *src, Py_ssize_t sr
 
     t = 0;
     pt = (PY_UINT8_T *)&t;
-    m = (PY_UINT8_T *)in;
+    m = in;
     switch (src_sz) {
         case 7: pt[6] = m[6];
         case 6: pt[5] = m[5];