diff --git a/library/common.h b/library/common.h
index c20f6b260e..ec30a7da1b 100644
--- a/library/common.h
+++ b/library/common.h
@@ -165,7 +165,10 @@ static inline const unsigned char *mbedtls_buffer_offset_const(
  * \param   b Pointer to input (buffer of at least \p n bytes)
  * \param   n Number of bytes to process.
  */
-inline void mbedtls_xor(unsigned char *r, const unsigned char *a, const unsigned char *b, size_t n)
+static inline void mbedtls_xor(unsigned char *r,
+                               const unsigned char *a,
+                               const unsigned char *b,
+                               size_t n)
 {
     size_t i = 0;
 #if defined(MBEDTLS_EFFICIENT_UNALIGNED_ACCESS)