diff --git a/contrib/python-zstandard/c-ext/compressor.c b/contrib/python-zstandard/c-ext/compressor.c
--- a/contrib/python-zstandard/c-ext/compressor.c
+++ b/contrib/python-zstandard/c-ext/compressor.c
@@ -258,6 +258,9 @@ static PyObject* ZstdCompressor_copy_str
 		return NULL;
 	}
 
+	/* Prevent free on uninitialized memory in finally. */
+	output.dst = NULL;
+
 	cstream = CStream_from_ZstdCompressor(self, sourceSize);
 	if (!cstream) {
 		res = NULL;
diff --git a/contrib/python-zstandard/c-ext/decompressor.c b/contrib/python-zstandard/c-ext/decompressor.c
--- a/contrib/python-zstandard/c-ext/decompressor.c
+++ b/contrib/python-zstandard/c-ext/decompressor.c
@@ -165,6 +165,9 @@ static PyObject* Decompressor_copy_strea
 		return NULL;
 	}
 
+	/* Prevent free on uninitialized memory in finally. */
+	output.dst = NULL;
+
 	dstream = DStream_from_ZstdDecompressor(self);
 	if (!dstream) {
 		res = NULL;