diff --git a/src/liblzma/check/crc32.c b/src/liblzma/check/crc32.c
index 091e1422..698cf768 100644
--- a/src/liblzma/check/crc32.c
+++ b/src/liblzma/check/crc32.c
@@ -18,7 +18,7 @@
 // If you make any changes, do some bench marking! Seemingly unrelated
 // changes can very easily ruin the performance (and very probably is
 // very compiler dependent).
-extern uint32_t
+extern LZMA_API uint32_t
 lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
 {
 	crc = ~crc;
diff --git a/src/liblzma/check/crc64.c b/src/liblzma/check/crc64.c
index e31bc7ff..00fbfd53 100644
--- a/src/liblzma/check/crc64.c
+++ b/src/liblzma/check/crc64.c
@@ -23,7 +23,7 @@
 
 
 // See comments in crc32.c.
-extern uint64_t
+extern LZMA_API uint64_t
 lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc)
 {
 	crc = ~crc;