diff --git a/BROKEN_SHADERS.md b/BROKEN_SHADERS.md
index 632b2e2..0e2d70d 100644
--- a/BROKEN_SHADERS.md
+++ b/BROKEN_SHADERS.md
@@ -5,7 +5,7 @@ The following shaders are known to be broken due to various issues.
 
 This list is updated as of [slang-shaders@`356678e`](https://github.com/libretro/slang-shaders/commit/356678ec53ca940a53fa509eff0b65bb63a403bb)
 
-## Parsing errors
+## Broken due to parsing errors
 librashader's preset parser is somewhat stricter than RetroArch in what it accepts. All shaders and textures in a preset must 
 resolve to a fully canonical path to properly parse. The following shaders have broken paths.
 
@@ -40,3 +40,9 @@ librashader's parser is fuzzed with slang-shaders and will accept invalid keys l
 to account for shader presets that use these invalid constructs. No known shader presets fail to parse due to syntax errors 
 that haven't already been accounted for.
 
+## Broken due to preprocessing errors
+
+The preprocessor resolves `#include` pragmas in each `.slang` shader and recursively flattens files into a single compute unit.
+
+* `misc/shaders/glass.slang`: Missing `misc/include/img/param_floats.h`.
+  * Looks like this was moved too deep, it references `../include/img/param_floats.h`, but the shader lives in the `misc/shaders/` folder.
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
index 6a4be07..0c0088e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -793,6 +793,7 @@ dependencies = [
  "librashader-common",
  "librashader-presets",
  "nom",
+ "rayon",
  "rustc-hash",
  "thiserror",
 ]
diff --git a/librashader-preprocess/Cargo.toml b/librashader-preprocess/Cargo.toml
index 6bfe47d..5e78055 100644
--- a/librashader-preprocess/Cargo.toml
+++ b/librashader-preprocess/Cargo.toml
@@ -24,4 +24,5 @@ line_directives = []
 
 [dev-dependencies]
 glob = "0.3.1"
-librashader-presets = { version = "0.1.0-beta.16", path = "../librashader-presets"}
\ No newline at end of file
+librashader-presets = { version = "0.1.0-beta.16", path = "../librashader-presets"}
+rayon = "1.6.1"
\ No newline at end of file
diff --git a/librashader-preprocess/tests/parse_all.rs b/librashader-preprocess/tests/parse_all.rs
index 8ea0991..fe45162 100644
--- a/librashader-preprocess/tests/parse_all.rs
+++ b/librashader-preprocess/tests/parse_all.rs
@@ -1,18 +1,23 @@
 use glob::glob;
-use librashader_preprocess::{PreprocessError, ShaderSource};
+use librashader_preprocess::ShaderSource;
 use librashader_presets::ShaderPreset;
+use rayon::prelude::*;
+
 #[test]
 fn preprocess_all_slang_presets_parsed() {
     for entry in glob("../test/slang-shaders/**/*.slangp").unwrap() {
         if let Ok(path) = entry {
             if let Ok(preset) = ShaderPreset::try_parse(&path) {
-                for shader in preset.shaders {
-                    ShaderSource::load(&shader.name).expect(&format!(
-                        "Failed to preprocess shader {} from preset {}",
-                        shader.name.display(),
-                        path.display()
-                    ));
-                }
+                preset.shaders.into_par_iter().for_each(|shader| {
+                    if let Err(e) = ShaderSource::load(&shader.name) {
+                        println!(
+                            "Failed to preprocess shader {} from preset {}: {:?}",
+                            shader.name.display(),
+                            path.display(),
+                            e
+                        );
+                    }
+                })
             }
         }
     }