diff --git a/headers/build/BeOSBuildCompatibility.h b/headers/build/BeOSBuildCompatibility.h
index 6a84253644..7dda8b56e2 100644
--- a/headers/build/BeOSBuildCompatibility.h
+++ b/headers/build/BeOSBuildCompatibility.h
@@ -16,6 +16,10 @@ extern "C" {
 extern size_t   strlcpy(char *dest, const char *source, size_t length);
 extern size_t	strlcat(char *dest, const char *source, size_t length);
 
+#ifdef HAIKU_HOST_PLATFORM_FREEBSD
+extern size_t	strnlen(const char *string, size_t length);
+#endif
+
 // BeOS only
 extern ssize_t  read_pos(int fd, off_t pos, void *buffer, size_t count);
 extern ssize_t  write_pos(int fd, off_t pos, const void *buffer,size_t count);
diff --git a/src/build/libroot/Jamfile b/src/build/libroot/Jamfile
index addee044ca..f1df1e9b14 100644
--- a/src/build/libroot/Jamfile
+++ b/src/build/libroot/Jamfile
@@ -32,10 +32,11 @@ BuildPlatformSharedLibrary libroot_build.so :
 
 	strlcpy.c
 	strlcat.c
+	strnlen.c
 
 	:
 	$(HOST_LIBSTDC++)
 ;
 
-SEARCH on [ FGristFiles strlcat.c strlcpy.c ]
+SEARCH on [ FGristFiles strlcat.c strlcpy.c strnlen.c ]
 	= [ FDirName $(HAIKU_TOP) src system libroot posix string ] ;