diff --git a/src/cairo-output-stream.c b/src/cairo-output-stream.c
index 5bce0e343..6d9c733c9 100644
--- a/src/cairo-output-stream.c
+++ b/src/cairo-output-stream.c
@@ -236,7 +236,7 @@ _cairo_dtostr (char *buffer, size_t size, double d)
     if (d == 0.0)
 	d = 0.0;
 
-    snprintf (buffer, size, "%f", d);
+    snprintf (buffer, size, "%.18f", d);
 
     locale_data = localeconv ();
     decimal_point = locale_data->decimal_point;