diff --git a/coders/tiff.c b/coders/tiff.c
index bd5c25c..4d3e961 100644
--- a/coders/tiff.c
+++ b/coders/tiff.c
@@ -2458,7 +2458,7 @@
         float
           rational;
 
-        rational=InterpretLocaleValue(value,(char **) NULL);
+        rational=StringToDouble(value,(char **) NULL);
         (void) TIFFSetField(tiff,exif_info[i].tag,rational);
         break;
       }