diff --git a/src/validation.jl b/src/validation.jl
index cb671ca..3e3cb2d 100644
--- a/src/validation.jl
+++ b/src/validation.jl
@@ -589,7 +589,7 @@ _is_type(::Real, ::Val{:number}) = true
 _is_type(::Nothing, ::Val{:null}) = true
 _is_type(::Missing, ::Val{:null}) = true
 _is_type(::AbstractDict, ::Val{:object}) = true
-_is_type(::String, ::Val{:string}) = true
+_is_type(::AbstractString, ::Val{:string}) = true
 # Note that Julia treat's Bool <: Number, but JSON-Schema distinguishes them.
 _is_type(::Bool, ::Val{:number}) = false
 _is_type(::Bool, ::Val{:integer}) = false
@@ -726,7 +726,7 @@ end
 
 # 6.3.1
 function _validate(
-    x::String,
+    x::AbstractString,
     schema,
     ::Val{:maxLength},
     val::Union{Integer,Float64},
@@ -740,7 +740,7 @@ end
 
 # 6.3.2
 function _validate(
-    x::String,
+    x::AbstractString,
     schema,
     ::Val{:minLength},
     val::Union{Integer,Float64},
@@ -754,7 +754,7 @@ end
 
 # 6.3.3
 function _validate(
-    x::String,
+    x::AbstractString,
     schema,
     ::Val{:pattern},
     val::String,
diff --git a/test/runtests.jl b/test/runtests.jl
index 3ef77c0..da335ba 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -14,6 +14,7 @@ import ZipFile
 
 include("additional_patterns.jl")
 include("integer_floats.jl")
+include("string_instances.jl")
 
 const TEST_SUITE_URL = "https://github.com/json-schema-org/JSON-Schema-Test-Suite/archive/23.1.0.zip"
 
diff --git a/test/string_instances.jl b/test/string_instances.jl
new file mode 100644
index 0000000..79df65c
--- /dev/null
+++ b/test/string_instances.jl
@@ -0,0 +1,57 @@
+@testset "AbstractString instances" begin
+    for wrap in (identity, s -> SubString(s), s -> LazyString("", s))
+        text = wrap("αβ")
+        @test isvalid(JSONSchema.schema(typeof(text)), text)
+        @test isvalid(JSONSchema.Schema(Dict("type" => "string")), text)
+        nullable = JSONSchema.Schema(Dict("type" => ["string", "null"]))
+        @test isvalid(nullable, text)
+        @test isvalid(nullable, nothing)
+
+        for (keyword, limit, value, expected) in (
+            ("maxLength", 2, "αβ", true),
+            ("maxLength", 1, "αβ", false),
+            ("maxLength", 0, "", true),
+            ("minLength", 1, "", false),
+            ("minLength", 2, "αβ", true),
+            ("minLength", 3, "αβ", false),
+            ("maxLength", 1, "e\u0301", false),
+        )
+            schema = JSONSchema.Schema(Dict(keyword => limit))
+            @test isvalid(schema, wrap(value)) == expected
+        end
+        for (pattern, value, expected) in (
+            (raw"^αβ$", "αβ", true),
+            ("^β", "αβ", false),
+            ("β", "αβ", true),
+            ("", "", true),
+        )
+            schema = JSONSchema.Schema(Dict("pattern" => pattern))
+            @test isvalid(schema, wrap(value)) == expected
+        end
+
+        for (rule, bad, reason) in (
+            (Dict("maxLength" => 1), "αβ", "maxLength"),
+            (Dict("minLength" => 3), "αβ", "minLength"),
+            (Dict("pattern" => "^z"), "αβ", "pattern"),
+        )
+            schema = JSONSchema.Schema(
+                Dict("properties" => Dict("names" => Dict("items" => rule))),
+            )
+            issue = JSONSchema.validate(schema, Dict("names" => [wrap(bad)]))
+            @test issue isa JSONSchema.SingleIssue &&
+                  issue.reason == reason &&
+                  JSONSchema.json_pointer(issue) == "#/names/0"
+        end
+        typed = JSONSchema.Schema(Dict("type" => "string", "minLength" => 2))
+        @test isvalid(typed, text)
+        @test !isvalid(typed, wrap("α"))
+    end
+
+    for data in (1, true, nothing, ["αβ"])
+        @test !isvalid(JSONSchema.Schema(Dict("type" => "string")), data)
+        @test isvalid(
+            JSONSchema.Schema(Dict("minLength" => 5, "pattern" => "^z")),
+            data,
+        )
+    end
+end