diff --git a/src/gallium/drivers/swr/rasterizer/common/os.h b/src/gallium/drivers/swr/rasterizer/common/os.h
index cc13936d8e9..b949625ae73 100644
--- a/src/gallium/drivers/swr/rasterizer/common/os.h
+++ b/src/gallium/drivers/swr/rasterizer/common/os.h
@@ -106,6 +106,7 @@ static inline void AlignedFree(void* p)
 #endif
 
 #if !defined(_WIN64)
+extern "C" {
 inline unsigned char _BitScanForward64(unsigned long* Index, uint64_t Mask)
 {
 #ifdef __GNUC__
@@ -131,6 +132,7 @@ inline unsigned char _BitScanReverse64(unsigned long* Index, uint64_t Mask)
 #endif
     return (Mask != 0);
 }
+}
 #endif
 
 #elif defined(__APPLE__) || defined(FORCE_LINUX) || defined(__linux__) || defined(__gnu_linux__)