diff --git a/cutils.c b/cutils.c
index 56982df..396bc71 100644
--- a/cutils.c
+++ b/cutils.c
@@ -600,7 +600,7 @@ char const digits36[36] = "0123456789abcdefghijklmnopqrstuvwxyz";
         else \
             buf = (buf << 8) | (c)
 
-size_t u7toa_shift(char dest[minimum_length(8)], uint32_t n)
+static size_t u7toa_shift(char dest[minimum_length(8)], uint32_t n)
 {
     size_t len = 1;
     uint64_t buf = 0;
@@ -615,7 +615,7 @@ size_t u7toa_shift(char dest[minimum_length(8)], uint32_t n)
     return len;
 }
 
-size_t u07toa_shift(char dest[minimum_length(8)], uint32_t n, size_t len)
+static size_t u07toa_shift(char dest[minimum_length(8)], uint32_t n, size_t len)
 {
     size_t i;
     dest += len;