diff --git a/doc/src/manual/strings.md b/doc/src/manual/strings.md
index 5628c4fa96d81..ee2b3f9d71d54 100644
--- a/doc/src/manual/strings.md
+++ b/doc/src/manual/strings.md
@@ -1088,7 +1088,7 @@ julia> x[1]
 0x31
 
 julia> x[1] = 0x32
-ERROR: setindex! not defined for Base.CodeUnits{UInt8, String}
+ERROR: CanonicalIndexError: setindex! not defined for Base.CodeUnits{UInt8, String}
 [...]
 
 julia> Vector{UInt8}(x)