diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index f9e7e057f7e0f7..91d3e38c622d32 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1452,8 +1452,9 @@ pyexpat_encoding_create(const char *name, PyObject *mapping)
                         "_expat_decoding_table must be a 256-tuple of integers");
         return NULL;
     }
+    size_t name_len = strlen(name) + 1;
     pyexpat_encoding_info *info = (pyexpat_encoding_info *)PyMem_Malloc(
-        sizeof(pyexpat_encoding_info) + strlen(name) + 1);
+        sizeof(pyexpat_encoding_info) + name_len);
     if (info == NULL) {
         PyErr_NoMemory();
         return NULL;
@@ -1466,7 +1467,7 @@ pyexpat_encoding_create(const char *name, PyObject *mapping)
         }
         info->map[i] = j;
     }
-    strcpy(info->name, name);
+    memcpy(info->name, name, name_len);
     return info;
 }
 
diff --git a/tests/test_invariant_pyexpat.c b/tests/test_invariant_pyexpat.c
new file mode 100644
index 00000000000000..e380c6934bda3f
--- /dev/null
+++ b/tests/test_invariant_pyexpat.c
@@ -0,0 +1,12 @@
+#include <check.h>
+#include <stdlib.h>
+#include <string.h>
+#include <Python.h>
+#include "Modules/pyexpat.c"
+
+START_TEST(test_buffer_reads_never_exceed_declared_length)
+{
+    // Invariant: Buffer reads never exceed the declared length
+    const char *payloads[] = {
+        "valid",  // Valid input
+        "                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
\ No newline at end of file