diff --git a/CHANGELOG.md b/CHANGELOG.md
index d88c371b49..c304506308 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - The `init` step of the Action now supports `ram` and `threads` inputs to limit resource use of CodeQL extractors. These inputs also serve as defaults to the subsequent `analyze` step, which finalizes the database and executes queries. [#738](https://github.com/github/codeql-action/pull/738)
 - When used with CodeQL 2.7.1 or above, the Action now includes custom query help in the analysis results uploaded to GitHub code scanning, if available. To add help text for a custom query, create a Markdown file next to the `.ql` file containing the query, using the same base name but the file extension `.md`. [#804](https://github.com/github/codeql-action/pull/804)
+- The `upload-sarif` action now allows multiple uploads in a single job, as long as they have different categories. [#801](https://github.com/github/codeql-action/pull/801)
 
 ## 1.0.21 - 28 Oct 2021
 
diff --git a/lib/upload-lib.js b/lib/upload-lib.js
index 1c88a190ea..ba39dedbe8 100644
--- a/lib/upload-lib.js
+++ b/lib/upload-lib.js
@@ -274,13 +274,26 @@ async function uploadFiles(sarifFiles, repositoryNwo, commitOid, ref, analysisKe
 function validateUniqueCategory(category) {
     if (util.isActions()) {
         // This check only works on actions as env vars don't persist between calls to the runner
-        const sentinelEnvVar = `CODEQL_UPLOAD_SARIF + ${category ? `_${category}` : ""}`;
+        const sentinelEnvVar = `CODEQL_UPLOAD_SARIF + ${category ? `_${sanitize(category)}` : ""}`;
         if (process.env[sentinelEnvVar]) {
             throw new Error("Aborting upload: only one run of the codeql/analyze or codeql/upload-sarif actions is allowed per job per category. " +
-                "Please specify a unique `category` to call this action multiple times.");
+                "Please specify a unique `category` to call this action multiple times. " +
+                `Category: ${category ? category : "(none)"}`);
         }
         core.exportVariable(sentinelEnvVar, sentinelEnvVar);
     }
 }
 exports.validateUniqueCategory = validateUniqueCategory;
+/**
+ * Santizes a string to be used as an environment variable name.
+ * This will replace all non-alphanumeric characters with underscores.
+ * There could still be some false category clashes if two uploads
+ * occur that differ only in their non-alphanumeric characters. This is
+ * unlikely.
+ *
+ * @param str the initial value to sanitize
+ */
+function sanitize(str) {
+    return str.replace(/[^a-zA-Z0-9_]/g, "_");
+}
 //# sourceMappingURL=upload-lib.js.map
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