diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index fc8b954f..2acb39e3 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -38,7 +38,10 @@ jobs:
             ${{ runner.os }}-
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
-      - name: Bounds check
+      - name: Coverage off  # `empty_func` test doesn't work as intended with `coverage=true`
+        if: ${{ matrix.os == 'ubuntu-latest' }}
+        run: julia --project -e 'using Pkg; Pkg.test("Cthulhu"; coverage=false)'
+      - name: Bounds/DCE check
         if: ${{ matrix.os == 'ubuntu-latest' }}
         run: julia --project --code-coverage -e 'using Pkg; Pkg.add(["Revise", "StaticArrays"]); cd("test"); include("runtests.jl")'
       - uses: julia-actions/julia-processcoverage@v1
diff --git a/src/Cthulhu.jl b/src/Cthulhu.jl
index 9a5bad23..bdd1348b 100644
--- a/src/Cthulhu.jl
+++ b/src/Cthulhu.jl
@@ -178,11 +178,20 @@ function lookup(interp::CthulhuInterpreter, mi::MethodInstance, optimize::Bool)
         end
     else
         codeinst = interp.opt[mi]
-        ir = Core.Compiler.copy(codeinst.inferred.ir::IRCode)
-        codeinf = ir
         rt = codeinst_rt(codeinst)
-        infos = ir.stmts.info
-        slottypes = ir.argtypes
+        codeinf0 = codeinst.inferred
+        if codeinf0 !== nothing
+            ir = Core.Compiler.copy(codeinf0.ir::IRCode)
+            codeinf = ir
+            infos = ir.stmts.info
+            slottypes = ir.argtypes
+        else
+            # This doesn't showed up as covered, but it is (see the CI test with `coverage=false`).
+            # But with coverage on, the empty function body isn't empty due to :code_coverage_effect expressions.
+            codeinf = nothing
+            infos = []
+            slottypes = Any[Base.unwrap_unionall(mi.specTypes).parameters...]
+        end
     end
     (codeinf, rt, infos, slottypes::Vector{Any})
 end
diff --git a/src/reflection.jl b/src/reflection.jl
index 1473edef..530d2ca5 100644
--- a/src/reflection.jl
+++ b/src/reflection.jl
@@ -76,7 +76,7 @@ function find_callsites(interp::CthulhuInterpreter, CI::Union{Core.CodeInfo, IRC
                     elseif isa(info, UnionSplitInfo)
                         return mapreduce(process_info, vcat, info.matches)
                     elseif isa(info, UnionSplitApplyCallInfo)
-                        return mapreduce(process_info, vcat, info.infos)
+                        return mapreduce(process_info, vcat, info.infos; init=Core.Compiler.ApplyCallInfo[])
                     elseif isa(info, ApplyCallInfo)
                         # XXX: This could probably use its own info. For now,
                         # we ignore any implicit iterate calls.
diff --git a/test/runtests.jl b/test/runtests.jl
index 82966119..39ca4b8b 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -25,12 +25,15 @@ end
 function process(@nospecialize(f), @nospecialize(TT); optimize=true)
     (interp, mi) = Cthulhu.mkinterp(f, TT)
     (ci, rt, infos, slottypes) = Cthulhu.lookup(interp, mi, optimize)
-    ci = Cthulhu.preprocess_ci!(ci, mi, optimize, Cthulhu.CthulhuConfig(dead_code_elimination=true))
+    if ci !== nothing
+        ci = Cthulhu.preprocess_ci!(ci, mi, optimize, Cthulhu.CthulhuConfig(dead_code_elimination=true))
+    end
     interp, ci, infos, mi, rt, slottypes
 end
 
 function find_callsites_by_ftt(@nospecialize(f), @nospecialize(TT=Tuple{}); optimize=true)
     interp, ci, infos, mi, _, slottypes = process(f, TT; optimize)
+    ci === nothing && return Cthulhu.Callsite[]
     callsites = Cthulhu.find_callsites(interp, ci, infos, mi, slottypes, optimize)
     return callsites
 end
@@ -44,12 +47,27 @@ function test()
     sum(rand(T, 100))
 end
 
-let callsites = find_callsites_by_ftt(test, Tuple{})
-    @test length(callsites) >= 4
+function empty_func(::Bool)
 end
 
-let callsites = find_callsites_by_ftt(test, Tuple{}; optimize=false)
+isordered(::Type{T}) where {T<:AbstractDict} = false
+
+@testset "Callsites" begin
+    callsites = find_callsites_by_ftt(test, Tuple{})
+    @test length(callsites) >= 4
+
+    callsites = find_callsites_by_ftt(test, Tuple{}; optimize=false)
     @test length(callsites) == 4
+
+    callsites = find_callsites_by_ftt(empty_func, Tuple{Bool}; optimize=true)
+    @test isempty(callsites)
+
+    # Some weird methods get inferred
+    callsites = find_callsites_by_ftt(iterate, (Base.IdSet{Any}, Union{}); optimize=false)
+    @test callsites[1].info isa Cthulhu.ConstPropCallInfo
+
+    # Broken stuff in Julia
+    @test_broken find_callsites_by_ftt(Core.Compiler._limit_type_size, Tuple{Any, Type{Any}, Core.SimpleVector, Int, Int})  # ssair/ir.jl bug
 end
 
 @testset "Expr heads" begin