diff --git a/flang/lib/Lower/Allocatable.cpp b/flang/lib/Lower/Allocatable.cpp
index 460ed62d5337f..e7a6c4df40045 100644
--- a/flang/lib/Lower/Allocatable.cpp
+++ b/flang/lib/Lower/Allocatable.cpp
@@ -629,6 +629,10 @@ class AllocateStmtHelper {
     unsigned allocatorIdx = Fortran::lower::getAllocatorIdx(alloc.getSymbol());
     fir::ExtendedValue exv = isSource ? sourceExv : moldExv;
 
+    if (const Fortran::semantics::Symbol *sym{GetLastSymbol(sourceExpr)})
+      if (Fortran::semantics::IsCUDADevice(*sym))
+        TODO(loc, "CUDA Fortran: allocate with device source");
+
     // Generate a sequence of runtime calls.
     errorManager.genStatCheck(builder, loc);
     genAllocateObjectInit(box, allocatorIdx);
diff --git a/flang/test/Lower/CUDA/TODO/cuda-allocate-source-device.cuf b/flang/test/Lower/CUDA/TODO/cuda-allocate-source-device.cuf
new file mode 100644
index 0000000000000..3e59e2f01119e
--- /dev/null
+++ b/flang/test/Lower/CUDA/TODO/cuda-allocate-source-device.cuf
@@ -0,0 +1,9 @@
+! RUN: %not_todo_cmd bbc -emit-fir -fcuda -o - %s 2>&1 | FileCheck %s
+
+program main
+  implicit none
+  integer, device, allocatable :: a_d(:)
+  integer, allocatable :: a(:)
+! CHECK: not yet implemented: CUDA Fortran: allocate with device source
+  allocate(a, source=a_d)
+end program