diff --git a/jax/experimental/mosaic/gpu/examples/matmul.py b/jax/experimental/mosaic/gpu/examples/matmul.py
index 52d403cd0131..775b7c2ea898 100644
--- a/jax/experimental/mosaic/gpu/examples/matmul.py
+++ b/jax/experimental/mosaic/gpu/examples/matmul.py
@@ -132,7 +132,7 @@ def build_kernel(
   if stages < 2:
     raise ValueError(f"Need at least 2 stages, but got {stages=}")
   if not rhs_transpose and jnp.dtype(rhs_dtype).itemsize != 2:
-    raise ValueError("Transpose only supported for only happen for 16bit types")
+    raise ValueError(f"Transpose only supported for 16bit types (got: {rhs_transpose=}, {rhs_dtype=})")
   if swizzle not in {32, 64, 128}:
     raise ValueError(f"swizzle must be 32, 64, or 128, but got {swizzle=}")