diff --git a/Misc/NEWS b/Misc/NEWS
index f1d55dd0622..7611c070911 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -4501,6 +4501,10 @@ Tools/Demos
 Extension Modules
 -----------------
 
+- Issue #16847: Fixed improper use of _PyUnicode_CheckConsistency() in
+  non-pydebug builds. Several extension modules now compile cleanly when
+  assert()s are enabled in standard builds (-DDEBUG flag).
+
 - Issue #13840: The error message produced by ctypes.create_string_buffer
   when given a Unicode string has been fixed.
 
diff --git a/Modules/_json.c b/Modules/_json.c
index 68ebe994c9a..2e1659eb98f 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -210,7 +210,9 @@ ascii_escape_unicode(PyObject *pystr)
         }
     }
     output[chars++] = '"';
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(rval, 1));
+#endif
     return rval;
 }
 
diff --git a/Modules/_sha3/sha3module.c b/Modules/_sha3/sha3module.c
index 4c3c6db1322..32cd85a1efa 100644
--- a/Modules/_sha3/sha3module.c
+++ b/Modules/_sha3/sha3module.c
@@ -300,7 +300,9 @@ SHA3_hexdigest(SHA3object *self, PyObject *unused)
         c = (digest[i] & 0xf);
         hex_digest[j++] = Py_hexdigits[c];
     }
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(retval, 1));
+#endif
     return retval;
 }
 
diff --git a/Modules/md5module.c b/Modules/md5module.c
index 4ecbb06baf0..6e15a20ac6c 100644
--- a/Modules/md5module.c
+++ b/Modules/md5module.c
@@ -399,7 +399,9 @@ MD5_hexdigest(MD5object *self, PyObject *unused)
         c = (digest[i] & 0xf);
         hex_digest[j++] = Py_hexdigits[c];
     }
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(retval, 1));
+#endif
     return retval;
 }
 
diff --git a/Modules/sha1module.c b/Modules/sha1module.c
index ab93f68f0de..52ef8a92cbe 100644
--- a/Modules/sha1module.c
+++ b/Modules/sha1module.c
@@ -376,7 +376,9 @@ SHA1_hexdigest(SHA1object *self, PyObject *unused)
         c = (digest[i] & 0xf);
         hex_digest[j++] = Py_hexdigits[c];
     }
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(retval, 1));
+#endif
     return retval;
 }
 
diff --git a/Modules/sha256module.c b/Modules/sha256module.c
index 4abd1cd43a8..3274e7c76ff 100644
--- a/Modules/sha256module.c
+++ b/Modules/sha256module.c
@@ -456,7 +456,9 @@ SHA256_hexdigest(SHAobject *self, PyObject *unused)
         c = (digest[i] & 0xf);
         hex_digest[j++] = Py_hexdigits[c];
     }
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(retval, 1));
+#endif
     return retval;
 }
 
diff --git a/Modules/sha512module.c b/Modules/sha512module.c
index bfb022c3277..3e0f6cebc72 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -522,7 +522,9 @@ SHA512_hexdigest(SHAobject *self, PyObject *unused)
         c = (digest[i] & 0xf);
         hex_digest[j++] = Py_hexdigits[c];
     }
+#ifdef Py_DEBUG
     assert(_PyUnicode_CheckConsistency(retval, 1));
+#endif
     return retval;
 }