diff --git a/base/range.jl b/base/range.jl
index 9f5dd214d67bb..859f55aece01d 100644
--- a/base/range.jl
+++ b/base/range.jl
@@ -905,7 +905,10 @@ end
 
 ## indexing
 
-isassigned(r::AbstractRange, i::Int) = firstindex(r) <= i <= lastindex(r)
+function isassigned(r::AbstractRange, i::Integer)
+    i isa Bool && throw(ArgumentError("invalid index: $i of type Bool"))
+    firstindex(r) <= i <= lastindex(r)
+end
 
 _in_unit_range(v::UnitRange, val, i::Integer) = i > 0 && val <= v.stop && val >= v.start
 
diff --git a/test/ranges.jl b/test/ranges.jl
index 0e195f5dde24e..27a74ac854e9f 100644
--- a/test/ranges.jl
+++ b/test/ranges.jl
@@ -2498,3 +2498,12 @@ end
     # a case that using mul_with_overflow & add_with_overflow might get wrong:
     @test (-10:2:typemax(Int))[typemax(Int)÷2+2] == typemax(Int)-9
 end
+
+@testset "isassigned" begin
+    for (r, val) in ((1:3, 3), (1:big(2)^65, big(2)^65))
+        @test isassigned(r, lastindex(r))
+        # test that the indexing actually succeeds
+        @test r[end] == val
+        @test_throws ArgumentError isassigned(r, true)
+    end
+end