diff --git a/src/liblzma/common/common.c b/src/liblzma/common/common.c
index 07b1d476..0408e153 100644
--- a/src/liblzma/common/common.c
+++ b/src/liblzma/common/common.c
@@ -182,6 +182,20 @@ lzma_code(lzma_stream *strm, lzma_action action)
 			|| !strm->internal->supported_actions[action])
 		return LZMA_PROG_ERROR;
 
+	// Check if unsupported members have been set to non-zero or non-NULL,
+	// which would indicate that some new feature is wanted.
+	if (strm->reserved_ptr1 != NULL
+			|| strm->reserved_ptr2 != NULL
+			|| strm->reserved_ptr3 != NULL
+			|| strm->reserved_ptr4 != NULL
+			|| strm->reserved_int1 != 0
+			|| strm->reserved_int2 != 0
+			|| strm->reserved_int3 != 0
+			|| strm->reserved_int4 != 0
+			|| strm->reserved_enum1 != LZMA_RESERVED_ENUM
+			|| strm->reserved_enum2 != LZMA_RESERVED_ENUM)
+		return LZMA_OPTIONS_ERROR;
+
 	switch (strm->internal->sequence) {
 	case ISEQ_RUN:
 		switch (action) {