diff --git a/src/flint/flint_base/flint_base.pyx b/src/flint/flint_base/flint_base.pyx
index 375486dc..84f3ae97 100644
--- a/src/flint/flint_base/flint_base.pyx
+++ b/src/flint/flint_base/flint_base.pyx
@@ -981,7 +981,7 @@ cdef class flint_mpoly(flint_elem):
             5*a
         """
         cdef:
-            slong *c_mapping
+            slong *c_mapping = NULL
             slong i
 
         ctx = self.context()
@@ -1001,7 +1001,7 @@ cdef class flint_mpoly(flint_elem):
             }
 
         try:
-            c_mapping = <slong *> libc.stdlib.malloc(ctx.nvars() * sizeof(slong *))
+            c_mapping = <slong *> libc.stdlib.malloc(ctx.nvars() * sizeof(slong))
             if c_mapping is NULL:
                 raise MemoryError("malloc returned a null pointer")
 
diff --git a/src/flint/types/_gr.pyx b/src/flint/types/_gr.pyx
index a555f367..3c1128d3 100644
--- a/src/flint/types/_gr.pyx
+++ b/src/flint/types/_gr.pyx
@@ -1815,7 +1815,7 @@ cdef class gr(flint_scalar):
             raise NotImplementedError("Cannot compare gr with >=")
             # res = self._ge(other_gr)
         else:
-            assert False, "Invalid rich comparison operator"
+            raise RuntimeError("Invalid rich comparison operator")
 
         return truth_to_py(res)
 
diff --git a/src/flint/types/fmpz.pxd b/src/flint/types/fmpz.pxd
index 4477daf0..165f8abc 100644
--- a/src/flint/types/fmpz.pxd
+++ b/src/flint/types/fmpz.pxd
@@ -4,12 +4,11 @@ from flint.utils.conversion cimport chars_from_str
 from flint.flintlib.types.flint cimport slong, ulong, pylong_as_slong
 from flint.flintlib.types.flint cimport PyObject
 from flint.flintlib.functions.fmpz cimport fmpz_t, fmpz_set_si, fmpz_set_signed_ui_array
-import sys
 
 cdef int fmpz_set_any_ref(fmpz_t x, obj)
 cdef fmpz_get_intlong(fmpz_t x)
 
-cdef int is_big_endian = int(sys.byteorder == "big")
+cdef int is_big_endian
 
 cdef inline ulong ulong_from_little_endian(unsigned char *ptr):
     # Read a ulong from little-endian bytes
diff --git a/src/flint/types/fmpz.pyx b/src/flint/types/fmpz.pyx
index 390282aa..2d6e3cf1 100644
--- a/src/flint/types/fmpz.pyx
+++ b/src/flint/types/fmpz.pyx
@@ -13,6 +13,9 @@ from flint.flintlib.functions.arith cimport *
 from flint.flintlib.functions.partitions cimport *
 
 from flint.utils.flint_exceptions import DomainError
+import sys
+
+is_big_endian = int(sys.byteorder == "big")
 
 cdef fmpz_get_intlong(fmpz_t x):
     """