diff --git a/src/llvm_abi.cpp b/src/llvm_abi.cpp
index da72ecd67..37df13b2c 100644
--- a/src/llvm_abi.cpp
+++ b/src/llvm_abi.cpp
@@ -726,13 +726,19 @@ namespace lbAbiAmd64SysV {
 	gb_internal bool is_aggregate(LLVMTypeRef type) {
 		// A single-member wrapper is passed like its member, but only while that
 		// member still fits one eightbyte. `struct{i128}` needs two registers and
-		// goes to memory when they are gone, where a bare `i128` does not -- clang
-		// emits `byval align 16` for the struct and a plain `i128` for the scalar.
+		// goes to memory when they are gone. A bare `i128` does not; clang emits
+		// `byval align 16` for the struct and a plain `i128` for the scalar.
 		LLVMTypeKind kind = LLVMGetTypeKind(type);
 		switch (kind) {
 		case LLVMStructTypeKind:
 			if (LLVMCountStructElementTypes(type) == 1) {
 				LLVMTypeRef elem = LLVMStructGetTypeAtIndex(type, 0);
+				// A VECTOR member keeps the wrapper an aggregate whatever its size:
+				// LLVM gives a vector its own oversized stack slot, so an unwrapped
+				// `struct{#simd[2]f32}` takes 16 bytes where the ABI wants 8.
+				if (LLVMGetTypeKind(elem) == LLVMVectorTypeKind) {
+					return true;
+				}
 				return lb_sizeof(elem) > 8 || is_aggregate(elem);
 			}
 			return true;
diff --git a/tests/abi/gen.py b/tests/abi/gen.py
index bf2d8b50b..4a9c86163 100644
--- a/tests/abi/gen.py
+++ b/tests/abi/gen.py
@@ -372,10 +372,13 @@ def build():
     add("zarr",  "struct { z: [0]f32 }",   "struct { float z[0]; }",  [], tier=TIER_GNU)
 
     # --- an array OF vectors, and a vector wider than one register
+    # The C paths index the vector array directly; only the ODIN side needs the
+    # hatch.
     add("av2_f32",
         "struct { a: [2]#simd[4]f32 }",
         "struct { rx_v4f a[2]; }",
-        [], tier=TIER_GNU,
+        [leaf2("", f"a[{i // 4}][{i % 4}]", "f32", f"{i + 1}.5") for i in range(8)],
+        tier=TIER_GNU,
         odin_set=["{}.a[0] = {1.5, 2.5, 3.5, 4.5}", "{}.a[1] = {5.5, 6.5, 7.5, 8.5}"],
         odin_get=[("simd.extract({}.a[0], 0)", "f32(1.5)"),
                   ("simd.extract({}.a[1], 3)", "f32(8.5)")])