diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index cbc734c..86727d1 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -27,7 +27,7 @@ jobs:
         run:
           go test -v -tags=llvm${{ matrix.llvm }}
       - name: Test default LLVM
-        if: matrix.llvm == 19
+        if: matrix.llvm == 21
         run:
           go test -v
   test-linux:
@@ -52,7 +52,7 @@ jobs:
         run:
           go test -v -tags=llvm${{ matrix.llvm }}
       - name: Test default LLVM
-        if: matrix.llvm == 19
+        if: matrix.llvm == 21
         run:
           go test -v
   test-windows:
@@ -169,7 +169,7 @@ jobs:
           gcc --version
           go test -v -tags=llvm${{ matrix.llvm }}
       - name: Test default LLVM
-        if: matrix.llvm == 19
+        if: matrix.llvm == 21
         shell: msys2 {0}
         run: |
           set -euo pipefail
@@ -202,6 +202,6 @@ jobs:
         run:
           go test -v -tags=llvm${{ matrix.llvm }}
       - name: Test default LLVM
-        if: matrix.llvm == 19
+        if: matrix.llvm == 21
         run:
           go test -v
diff --git a/README.markdown b/README.markdown
index 3884324..3abfe6e 100644
--- a/README.markdown
+++ b/README.markdown
@@ -16,8 +16,8 @@ Currently supported:
   * LLVM 22, 21, 20, 19, 18, 17, 16, 15 and 14 in an MSYS2 MINGW64 environment on Windows (see the setup below).
   * Any of the above versions with a manually built LLVM through the `byollvm` build tag. You need to set up `CFLAGS`/`LDFLAGS` etc yourself in this case.
 
-You can select the LLVM version using a build tag, for example `-tags=llvm17`
-to use LLVM 17.
+LLVM 21 is selected by default. You can select another LLVM version using a
+build tag, for example `-tags=llvm19` to use LLVM 19.
 
 ## Usage
 
@@ -30,7 +30,7 @@ You can use build tags to select a LLVM version. For example, use `-tags=llvm15`
 ### Windows (MSYS2 MINGW64)
 
 The Windows bindings expect `pkg-config` metadata named after the selected LLVM
-major version, such as `llvm-19`. After installing a MinGW-compatible LLVM,
+major version, such as `llvm-21`. After installing a MinGW-compatible LLVM,
 `mingw-w64-x86_64-gcc`, and `mingw-w64-x86_64-pkgconf` in a MINGW64
 environment, generate that file from `llvm-config`:
 
diff --git a/ir.go b/ir.go
index 6cc60e5..4db5b1b 100644
--- a/ir.go
+++ b/ir.go
@@ -678,6 +678,7 @@ func (t Type) StructSetBody(elementTypes []Type, packed bool) {
 }
 
 func (t Type) IsStructPacked() bool         { return C.LLVMIsPackedStruct(t.C) != 0 }
+func (t Type) IsStructOpaque() bool         { return C.LLVMIsOpaqueStruct(t.C) != 0 }
 func (t Type) StructElementTypesCount() int { return int(C.LLVMCountStructElementTypes(t.C)) }
 func (t Type) StructElementTypes() []Type {
 	out := make([]Type, t.StructElementTypesCount())
diff --git a/ir_test.go b/ir_test.go
index 0a9d5e8..b28f737 100644
--- a/ir_test.go
+++ b/ir_test.go
@@ -18,6 +18,21 @@ import (
 	"testing"
 )
 
+func TestStructIsOpaque(t *testing.T) {
+	ctx := NewContext()
+	defer ctx.Dispose()
+
+	typ := ctx.StructCreateNamed("T")
+	if !typ.IsStructOpaque() {
+		t.Fatal("new named struct is not opaque")
+	}
+
+	typ.StructSetBody(nil, false)
+	if typ.IsStructOpaque() {
+		t.Fatal("defined empty named struct is opaque")
+	}
+}
+
 func testAttribute(t *testing.T, name string) {
 	ctx := NewContext()
 	mod := ctx.NewModule("")
diff --git a/llvm_config_llvm19.go b/llvm_config_llvm19.go
index 83a0f1a..29692bd 100644
--- a/llvm_config_llvm19.go
+++ b/llvm_config_llvm19.go
@@ -1,5 +1,5 @@
-//go:build !byollvm && !llvm14 && !llvm15 && !llvm16 && !llvm17 && !llvm18 && !llvm20 && !llvm21 && !llvm22
-// +build !byollvm,!llvm14,!llvm15,!llvm16,!llvm17,!llvm18,!llvm20,!llvm21,!llvm22
+//go:build !byollvm && llvm19
+// +build !byollvm,llvm19
 
 package llvm
 
diff --git a/llvm_config_llvm21.go b/llvm_config_llvm21.go
index bff0dba..602f460 100644
--- a/llvm_config_llvm21.go
+++ b/llvm_config_llvm21.go
@@ -1,4 +1,5 @@
-//go:build !byollvm && llvm21
+//go:build !byollvm && !llvm14 && !llvm15 && !llvm16 && !llvm17 && !llvm18 && !llvm19 && !llvm20 && !llvm22
+// +build !byollvm,!llvm14,!llvm15,!llvm16,!llvm17,!llvm18,!llvm19,!llvm20,!llvm22
 
 package llvm