diff --git a/lib/types.nix b/lib/types.nix
index e6f84176657..66e8aa272e8 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -549,12 +549,12 @@ rec {
       mkOptionType rec {
         name = "coercedTo";
         description = "${finalType.description} or ${coercedType.description} convertible to it";
-        check = x: finalType.check x || (coercedType.check x && finalType.check (coerceFunc x));
+        check = x: (coercedType.check x && finalType.check (coerceFunc x)) || finalType.check x;
         merge = loc: defs:
           let
             coerceVal = val:
-              if finalType.check val then val
-              else coerceFunc val;
+              if coercedType.check val then coerceFunc val
+              else val;
           in finalType.merge loc (map (def: def // { value = coerceVal def.value; }) defs);
         emptyValue = finalType.emptyValue;
         getSubOptions = finalType.getSubOptions;