diff --git a/src/CodeTracking.jl b/src/CodeTracking.jl
index 9e8e5f5..7355da5 100644
--- a/src/CodeTracking.jl
+++ b/src/CodeTracking.jl
@@ -114,6 +114,7 @@ Return the signatures of all methods whose definition spans the specified locati
 Returns `nothing` if there are no methods at that location.
 """
 function signatures_at(filename::AbstractString, line::Integer)
+    filename = abspath(filename)
     if occursin(juliabase, filename)
         rpath = postpath(filename, juliabase)
         id = PkgId(Base)
@@ -139,7 +140,7 @@ function signatures_at(filename::AbstractString, line::Integer)
             end
         end
     end
-    error("$filename not found, perhaps the package is not loaded")
+    error("$filename not found in internal data, perhaps the package is not loaded (or not loaded with `includet`)")
 end
 
 """
diff --git a/test/runtests.jl b/test/runtests.jl
index 84eea2d..db725ac 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -4,7 +4,7 @@ using CodeTracking
 using Test, InteractiveUtils
 # Note: ColorTypes needs to be installed, but note the intentional absence of `using ColorTypes`
 
-include("script.jl")
+isdefined(Main, :Revise) ? includet("script.jl") : include("script.jl")
 
 @testset "CodeTracking.jl" begin
     m = first(methods(f1))
@@ -87,5 +87,8 @@ end
         @test !isempty(sigs)
         sigs = signatures_at(Base.find_source_file(String(m.file)), m.line)
         @test !isempty(sigs)
+
+        # issue #23
+        @test !isempty(signatures_at("script.jl", 9))
     end
 end