diff --git a/gen/functions.cpp b/gen/functions.cpp
index a96a49cd508..fdc54582b6b 100644
--- a/gen/functions.cpp
+++ b/gen/functions.cpp
@@ -1046,6 +1046,8 @@ void DtoDefineFunction(FuncDeclaration *fd, bool linkageAvailableExternally) {
   }
 
   if (fd->ir->isDefined()) {
+    if (fd->llvmInternal == LLVMva_arg)
+      return;
     llvm::Function *func = getIrFunc(fd)->getLLVMFunc();
     assert(func);
     if (!linkageAvailableExternally &&
diff --git a/tests/compilable/va_arg.d b/tests/compilable/va_arg.d
new file mode 100644
index 00000000000..1d43be44585
--- /dev/null
+++ b/tests/compilable/va_arg.d
@@ -0,0 +1,10 @@
+// RUN: %ldc -mtriple=aarch64-none-elf -c %s
+// RUN: %ldc -mtriple=riscv64-unknown-elf -c %s
+
+alias va_list = void*;
+
+pragma(LDC_va_arg) T va_arg(T)(va_list ap);
+
+int foo(va_list ap) {
+    return va_arg!(int)(ap);
+}