diff --git a/src/codegen/wasm/abi.zig b/src/codegen/wasm/abi.zig
index 9f0b9b6dc9ebb7715d16839a6f42fd954d7787a2..5c88caddb98a35c6f192c647fb5d53eb032375a5 100644
--- a/src/codegen/wasm/abi.zig
+++ b/src/codegen/wasm/abi.zig
@@ -102,6 +102,13 @@ pub fn classifyTypeForLlvm(ty: Type, zcu: *const Zcu) LlvmClass {
             assert(layout.tag_size == 0);
             if (union_obj.field_types.len > 1) return .indirect;
             const first_field_ty = Type.fromInterned(union_obj.field_types.get(ip)[0]);
+            if (first_field_ty.zigTypeTag(zcu) == .array) {
+                switch (first_field_ty.arrayLenIncludingSentinel(zcu)) {
+                    0 => unreachable,
+                    1 => return classifyTypeForLlvm(first_field_ty.childType(zcu), zcu),
+                    else => {},
+                }
+            }
             return classifyTypeForLlvm(first_field_ty, zcu);
         },
         .error_union,
diff --git a/test/c_abi/cfuncs.c b/test/c_abi/cfuncs.c
index a259e23413a131b4e73b5f34329e1b2e6093f44d..110e5fd18dd4a5593c7004f439e85eed82c46a1d 100644
--- a/test/c_abi/cfuncs.c
+++ b/test/c_abi/cfuncs.c
@@ -15749,6 +15749,26 @@ void c_test_struct_array_5_f64(void) {
     zig_struct_array_5_f64((struct Struct_array_5_f64){ .a = { 6, 7, 8, 9, 10 } }, 11);
 }
 
+union Union_f64 {
+    double a;
+};
+
+union Union_f64 zig_ret_union_f64(void);
+void zig_union_f64(union Union_f64, size_t);
+
+union Union_f64 c_ret_union_f64(void) {
+    return (union Union_f64){ .a = 4 };
+}
+void c_union_f64(union Union_f64 s, size_t i) {
+    assert_or_panic(s.a == 5);
+    assert_or_panic(i == 6);
+}
+void c_test_union_f64(void) {
+    union Union_f64 s = zig_ret_union_f64();
+    assert_or_panic(s.a == 1);
+    zig_union_f64((union Union_f64){ .a = 2 }, 3);
+}
+
 struct Struct_u32_Union_u32_u32u32 {
     uint32_t a;
     union {
diff --git a/test/c_abi/main.zig b/test/c_abi/main.zig
index 4cc383805d755af213f3e84a2cb5447c0a5315f1..2286d838b86402f9e5e03c30e7db3732c2e3c3f4 100644
--- a/test/c_abi/main.zig
+++ b/test/c_abi/main.zig
@@ -16918,6 +16918,36 @@ test "struct [5]f64" {
     c_test_struct_array_5_f64();
 }
 
+const Union_f64 = extern union {
+    a: f64,
+};
+
+export fn zig_ret_union_f64() Union_f64 {
+    return .{ .a = 1 };
+}
+export fn zig_union_f64(s: Union_f64, i: usize) void {
+    expect(s.a == 2) catch @panic("test failure");
+    expect(i == 3) catch @panic("test failure");
+}
+
+extern fn c_ret_union_f64() Union_f64;
+extern fn c_union_f64(Union_f64, usize) void;
+extern fn c_test_union_f64() void;
+
+test "union f64" {
+    if (builtin.cpu.arch.isArm() and builtin.abi.float() == .soft) return error.SkipZigTest;
+    if (builtin.cpu.arch.isMIPS()) return error.SkipZigTest;
+    if (builtin.cpu.arch.isPowerPC()) return error.SkipZigTest;
+    if (builtin.cpu.arch.isRiscv32()) return error.SkipZigTest;
+    if (builtin.cpu.arch == .s390x) return error.SkipZigTest;
+    if (builtin.cpu.arch == .x86 and builtin.os.tag == .windows) return error.SkipZigTest;
+
+    const s = c_ret_union_f64();
+    try expect(s.a == 4);
+    c_union_f64(.{ .a = 5 }, 6);
+    c_test_union_f64();
+}
+
 const Struct_u32_Union_u32_u32u32 = extern struct {
     a: u32,
     b: extern union {