diff --git a/src/cgutils.cpp b/src/cgutils.cpp
index 60a8c7db5b8fb..37f2f6430ba9f 100644
--- a/src/cgutils.cpp
+++ b/src/cgutils.cpp
@@ -1023,7 +1023,7 @@ static void emit_typecheck(const jl_cgval_t &x, jl_value_t *type, const std::str
     //     return;
     // }
     Value *istype = emit_isa(x, type, &msg, ctx);
-    if (!isa<Constant>(istype)) {
+    if (!isa<ConstantInt>(istype)) {
         BasicBlock *failBB = BasicBlock::Create(jl_LLVMContext, "fail", ctx->f);
         BasicBlock *passBB = BasicBlock::Create(jl_LLVMContext, "pass");
         builder.CreateCondBr(istype, passBB, failBB);
diff --git a/test/core.jl b/test/core.jl
index f3c42b0875cfb..b9b808756ff6d 100644
--- a/test/core.jl
+++ b/test/core.jl
@@ -4792,3 +4792,7 @@ b21178(::F1,::F2) where {B1,B2,F1<:F21178{B1,<:Any},F2<:F21178{B2}} = F1,F2,B1,B
 a21172 = f21172(x) = 2x
 @test f21172(8) == 16
 @test a21172 === f21172
+
+# issue #21271
+f21271()::Tuple{Type{Int}, Type{Float64}} = (Int, Float64)
+@test_throws TypeError f21271()