diff --git a/src/pixie/internal.nim b/src/pixie/internal.nim
index b18212f..a2585f6 100644
--- a/src/pixie/internal.nim
+++ b/src/pixie/internal.nim
@@ -71,11 +71,17 @@ proc fillUnsafe*(
   else:
     var i = start
     when defined(amd64) and allowSimd:
+      # Align to 16 bytes
+      while i < (start + len) and (cast[uint](data[i].addr) and 15) != 0:
+        data[i] = rgbx
+        inc i
       # When supported, SIMD fill until we run out of room
-      let colorVec = mm_set1_epi32(cast[int32](rgbx))
-      for _ in 0 ..< len div 8:
-        mm_storeu_si128(data[i + 0].addr, colorVec)
-        mm_storeu_si128(data[i + 4].addr, colorVec)
+      let
+        colorVec = mm_set1_epi32(cast[int32](rgbx))
+        remaining = start + len - i
+      for _ in 0 ..< remaining div 8:
+        mm_store_si128(data[i + 0].addr, colorVec)
+        mm_store_si128(data[i + 4].addr, colorVec)
         i += 8
     else:
       when sizeof(int) == 8: