diff --git a/pyroaring/abstract_bitmap.pxi b/pyroaring/abstract_bitmap.pxi
index 786be9a..9608703 100644
--- a/pyroaring/abstract_bitmap.pxi
+++ b/pyroaring/abstract_bitmap.pxi
@@ -421,6 +421,7 @@ cdef class AbstractBitMap:
             return bitmaps[0] - bitmaps[1]
         else:
             result = BitMap(bitmaps[0])
+            result._h_val = 0
             for bm in bitmaps[1:]:
                 result -= bm
             return bitmaps[0].__class__(result)
@@ -474,6 +475,7 @@ cdef class AbstractBitMap:
             return bitmaps[0] & bitmaps[1]
         else:
             result = BitMap(bitmaps[0])
+            result._h_val = 0
             for bm in bitmaps[1:]:
                 result &= bm
             return bitmaps[0].__class__(result)
@@ -1332,6 +1334,7 @@ cdef class AbstractBitMap64:
             return bitmaps[0] - bitmaps[1]
         else:
             result = BitMap64(bitmaps[0])
+            result._h_val = 0
             for bm in bitmaps[1:]:
                 result -= bm
             return bitmaps[0].__class__(result)
@@ -1382,6 +1385,7 @@ cdef class AbstractBitMap64:
             return bitmaps[0] & bitmaps[1]
         else:
             result = BitMap64(bitmaps[0])
+            result._h_val = 0
             for bm in bitmaps[1:]:
                 result &= bm
             return bitmaps[0].__class__(result)
@@ -1469,4 +1473,4 @@ cdef class AbstractBitMap64:
         >>> BitMap64([3, 10, 12]).jaccard_index(BitMap64([3, 18]))
         0.25
         """
-        return croaring.roaring64_bitmap_jaccard_index(self._c_bitmap, other._c_bitmap)
\ No newline at end of file
+        return croaring.roaring64_bitmap_jaccard_index(self._c_bitmap, other._c_bitmap)