diff --git a/libs/vkd3d-shader/fx.c b/libs/vkd3d-shader/fx.c
index ff898e8f..1a64fc74 100644
--- a/libs/vkd3d-shader/fx.c
+++ b/libs/vkd3d-shader/fx.c
@@ -4376,7 +4376,8 @@ static int fx_4_parse(struct fx_parser *parser)
 
     if (parser->end - parser->ptr < header.unstructured_size)
     {
-        parser->failed = true;
+        fx_parser_error(parser, VKD3D_SHADER_ERROR_FX_INVALID_SIZE,
+                "Invalid unstructured data size %u.", header.unstructured_size);
         return -1;
     }
 
@@ -4432,7 +4433,8 @@ static int fx_5_parse(struct fx_parser *parser)
 
     if (parser->end - parser->ptr < header.unstructured_size)
     {
-        parser->failed = true;
+        fx_parser_error(parser, VKD3D_SHADER_ERROR_FX_INVALID_SIZE,
+                "Invalid unstructured data size %u.", header.unstructured_size);
         return -1;
     }
 
@@ -4465,7 +4467,11 @@ int fx_parse(const struct vkd3d_shader_compile_info *compile_info,
     vkd3d_string_buffer_init(&parser.buffer);
 
     if (parser.end - parser.start < sizeof(version))
+    {
+        fx_parser_error(&parser, VKD3D_SHADER_ERROR_FX_INVALID_SIZE,
+                "Source size %zu is smaller than the FX header size.", compile_info->source.size);
         return -1;
+    }
     version = *(uint32_t *)parser.ptr;
 
     switch (version)
diff --git a/libs/vkd3d-shader/vkd3d_shader_private.h b/libs/vkd3d-shader/vkd3d_shader_private.h
index 48176d85..3fe5959f 100644
--- a/libs/vkd3d-shader/vkd3d_shader_private.h
+++ b/libs/vkd3d-shader/vkd3d_shader_private.h
@@ -263,6 +263,7 @@ enum vkd3d_shader_error
     VKD3D_SHADER_ERROR_FX_NOT_IMPLEMENTED               = 11000,
     VKD3D_SHADER_ERROR_FX_INVALID_VERSION               = 11001,
     VKD3D_SHADER_ERROR_FX_INVALID_DATA                  = 11002,
+    VKD3D_SHADER_ERROR_FX_INVALID_SIZE                  = 11003,
 };
 
 enum vkd3d_shader_opcode