diff --git a/base/strings/unicode.jl b/base/strings/unicode.jl
index 9a44912946205..42a4106d0f52f 100644
--- a/base/strings/unicode.jl
+++ b/base/strings/unicode.jl
@@ -432,7 +432,7 @@ end
 """
     isdigit(c::AbstractChar) -> Bool
 
-Tests whether a character is a decimal digit (0-9).
+Tests whether a character is an ASCII decimal digit (`0`-`9`).
 
 See also: [`isletter`](@ref).