diff --git a/libs/vkd3d-shader/ir.c b/libs/vkd3d-shader/ir.c
index fd594bad..1b52f866 100644
--- a/libs/vkd3d-shader/ir.c
+++ b/libs/vkd3d-shader/ir.c
@@ -1510,6 +1510,10 @@ static void vsir_validate_register(struct validation_context *ctx,
     if (reg->dimension >= VSIR_DIMENSION_COUNT)
         validator_error(ctx, VKD3D_SHADER_ERROR_VSIR_INVALID_DIMENSION, "Invalid register dimension %#x.",
                 reg->dimension);
+
+    if (reg->idx_count > ARRAY_SIZE(reg->idx))
+        validator_error(ctx, VKD3D_SHADER_ERROR_VSIR_INVALID_INDEX_COUNT, "Invalid register index count %u.",
+                reg->idx_count);
 }
 
 static void vsir_validate_dst_param(struct validation_context *ctx,
diff --git a/libs/vkd3d-shader/vkd3d_shader_private.h b/libs/vkd3d-shader/vkd3d_shader_private.h
index f8d10061..8e744593 100644
--- a/libs/vkd3d-shader/vkd3d_shader_private.h
+++ b/libs/vkd3d-shader/vkd3d_shader_private.h
@@ -203,6 +203,7 @@ enum vkd3d_shader_error
     VKD3D_SHADER_ERROR_VSIR_INVALID_PRECISION           = 9007,
     VKD3D_SHADER_ERROR_VSIR_INVALID_DATA_TYPE           = 9008,
     VKD3D_SHADER_ERROR_VSIR_INVALID_DIMENSION           = 9009,
+    VKD3D_SHADER_ERROR_VSIR_INVALID_INDEX_COUNT         = 9010,
 };
 
 enum vkd3d_shader_opcode