diff --git a/fdlibm.h b/fdlibm.h
--- a/fdlibm.h
+++ b/fdlibm.h
@@ -16,16 +16,20 @@
 
 #ifndef mozilla_imported_fdlibm_h
 #define	mozilla_imported_fdlibm_h
 
 #ifndef M_PI_2
 #define	M_PI_2		1.57079632679489661923	/* pi/2 */
 #endif
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 double	fdlibm_acos(double);
 double	fdlibm_asin(double);
 double	fdlibm_atan(double);
 double	fdlibm_atan2(double, double);
 double	fdlibm_cos(double);
 double	fdlibm_sin(double);
 double	fdlibm_tan(double);
 
@@ -74,9 +76,13 @@ float	fdlibm_sqrtf(float);
 float	fdlibm_fabsf(float);
 float	fdlibm_floorf(float);
 float	fdlibm_hypotf(float, float);
 float	fdlibm_nearbyintf(float);
 float	fdlibm_rintf(float);
 float	fdlibm_scalbnf(float, int);
 float	fdlibm_truncf(float);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif /* !mozilla_imported_fdlibm_h */