diff --git a/src/gallium/frontends/rusticl/api/program.rs b/src/gallium/frontends/rusticl/api/program.rs
index 488ddd9411c..5c4ecc5d61f 100644
--- a/src/gallium/frontends/rusticl/api/program.rs
+++ b/src/gallium/frontends/rusticl/api/program.rs
@@ -48,10 +48,11 @@ unsafe impl CLInfo<cl_program_info> for cl_program {
             CL_PROGRAM_DEVICES => {
                 v.write_iter::<cl_device_id>(prog.devs.iter().map(|&d| cl_device_id::from_ptr(d)))
             }
-            CL_PROGRAM_IL => v.write::<&[u8]>(match &prog.src {
-                ProgramSourceType::Il(il) => il.to_bin(),
-                _ => &[],
-            }),
+            CL_PROGRAM_IL => match &prog.src {
+                ProgramSourceType::Il(il) => v.write::<&[u8]>(il.to_bin()),
+                // The spec _requires_ that we don't touch the buffer here.
+                _ => v.write_len_only::<&[u8]>(0),
+            },
             CL_PROGRAM_KERNEL_NAMES => v.write::<&str>(&prog.build_info().kernels().join(";")),
             CL_PROGRAM_NUM_DEVICES => v.write::<cl_uint>(prog.devs.len() as cl_uint),
             CL_PROGRAM_NUM_KERNELS => v.write::<usize>(prog.build_info().kernels().len()),