diff --git a/library/ecp.c b/library/ecp.c
index bedb67506..3a075c403 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -59,6 +59,14 @@
 #include <limits.h>
 #include <stdlib.h>
 
+#if defined(_MSC_VER) && !defined(inline)
+#define inline _inline
+#else
+#if defined(__ARMCC_VERSION) && !defined(inline)
+#define inline __inline
+#endif /* __ARMCC_VERSION */
+#endif /*_MSC_VER */
+
 #if defined(POLARSSL_SELF_TEST)
 /*
  * Counts of point addition and doubling operations.