diff --git a/lib/diagnostics.js b/lib/diagnostics.js
index 90a64accd..f83221c57 100644
--- a/lib/diagnostics.js
+++ b/lib/diagnostics.js
@@ -32,6 +32,8 @@ exports.makeDiagnostic = makeDiagnostic;
 function addDiagnostic(config, diagnostic) {
     const logger = (0, logging_1.getActionsLogger)();
     const diagnosticsPath = path_1.default.resolve(config.dbLocation, "diagnostic", "codeql-action");
+    // Create the directory if it doesn't exist yet.
+    (0, fs_1.mkdirSync)(diagnosticsPath, { recursive: true });
     const jsonPath = path_1.default.resolve(diagnosticsPath, `codeql-action-${diagnostic.timestamp}.json`);
     try {
         (0, fs_1.writeFileSync)(jsonPath, JSON.stringify(diagnostic));
diff --git a/lib/diagnostics.js.map b/lib/diagnostics.js.map
index 3342b869e..530299d99 100644
--- a/lib/diagnostics.js.map
+++ b/lib/diagnostics.js.map
@@ -1 +1 @@
-{"version":3,"file":"diagnostics.js","sourceRoot":"","sources":["../src/diagnostics.ts"],"names":[],"mappings":";;;;;;AAAA,2BAAmC;AACnC,gDAAwB;AAGxB,uCAA6C;AAmD7C;;;;;;;GAOG;AACH,SAAgB,cAAc,CAC5B,EAAU,EACV,IAAY,EACZ,OAA+C,SAAS;IAExD,OAAO;QACL,GAAG,IAAI;QACP,SAAS,EAAE,IAAI,EAAE,SAAS,IAAI,IAAI,IAAI,EAAE,CAAC,WAAW,EAAE;QACtD,MAAM,EAAE,EAAE,GAAG,IAAI,EAAE,MAAM,EAAE,EAAE,EAAE,IAAI,EAAE;KACtC,CAAC;AACJ,CAAC;AAVD,wCAUC;AAED;;;;;GAKG;AACH,SAAgB,aAAa,CAAC,MAAc,EAAE,UAA6B;IACzE,MAAM,MAAM,GAAG,IAAA,0BAAgB,GAAE,CAAC;IAClC,MAAM,eAAe,GAAG,cAAI,CAAC,OAAO,CAClC,MAAM,CAAC,UAAU,EACjB,YAAY,EACZ,eAAe,CAChB,CAAC;IACF,MAAM,QAAQ,GAAG,cAAI,CAAC,OAAO,CAC3B,eAAe,EACf,iBAAiB,UAAU,CAAC,SAAS,OAAO,CAC7C,CAAC;IAEF,IAAI;QACF,IAAA,kBAAa,EAAC,QAAQ,EAAE,IAAI,CAAC,SAAS,CAAC,UAAU,CAAC,CAAC,CAAC;KACrD;IAAC,OAAO,GAAG,EAAE;QACZ,MAAM,CAAC,OAAO,CAAC,mDAAmD,GAAG,EAAE,CAAC,CAAC;KAC1E;AACH,CAAC;AAjBD,sCAiBC"}
\ No newline at end of file
+{"version":3,"file":"diagnostics.js","sourceRoot":"","sources":["../src/diagnostics.ts"],"names":[],"mappings":";;;;;;AAAA,2BAA8C;AAC9C,gDAAwB;AAGxB,uCAA6C;AAmD7C;;;;;;;GAOG;AACH,SAAgB,cAAc,CAC5B,EAAU,EACV,IAAY,EACZ,OAA+C,SAAS;IAExD,OAAO;QACL,GAAG,IAAI;QACP,SAAS,EAAE,IAAI,EAAE,SAAS,IAAI,IAAI,IAAI,EAAE,CAAC,WAAW,EAAE;QACtD,MAAM,EAAE,EAAE,GAAG,IAAI,EAAE,MAAM,EAAE,EAAE,EAAE,IAAI,EAAE;KACtC,CAAC;AACJ,CAAC;AAVD,wCAUC;AAED;;;;;GAKG;AACH,SAAgB,aAAa,CAAC,MAAc,EAAE,UAA6B;IACzE,MAAM,MAAM,GAAG,IAAA,0BAAgB,GAAE,CAAC;IAClC,MAAM,eAAe,GAAG,cAAI,CAAC,OAAO,CAClC,MAAM,CAAC,UAAU,EACjB,YAAY,EACZ,eAAe,CAChB,CAAC;IAEF,gDAAgD;IAChD,IAAA,cAAS,EAAC,eAAe,EAAE,EAAE,SAAS,EAAE,IAAI,EAAE,CAAC,CAAC;IAEhD,MAAM,QAAQ,GAAG,cAAI,CAAC,OAAO,CAC3B,eAAe,EACf,iBAAiB,UAAU,CAAC,SAAS,OAAO,CAC7C,CAAC;IAEF,IAAI;QACF,IAAA,kBAAa,EAAC,QAAQ,EAAE,IAAI,CAAC,SAAS,CAAC,UAAU,CAAC,CAAC,CAAC;KACrD;IAAC,OAAO,GAAG,EAAE;QACZ,MAAM,CAAC,OAAO,CAAC,mDAAmD,GAAG,EAAE,CAAC,CAAC;KAC1E;AACH,CAAC;AArBD,sCAqBC"}
\ No newline at end of file
diff --git a/src/diagnostics.ts b/src/diagnostics.ts
index 39b9a1ad1..67cb29042 100644
--- a/src/diagnostics.ts
+++ b/src/diagnostics.ts
@@ -1,4 +1,4 @@
-import { writeFileSync } from "fs";
+import { mkdirSync, writeFileSync } from "fs";
 import path from "path";
 
 import { Config } from "./config-utils";
@@ -86,6 +86,10 @@ export function addDiagnostic(config: Config, diagnostic: DiagnosticMessage) {
     "diagnostic",
     "codeql-action",
   );
+
+  // Create the directory if it doesn't exist yet.
+  mkdirSync(diagnosticsPath, { recursive: true });
+
   const jsonPath = path.resolve(
     diagnosticsPath,
     `codeql-action-${diagnostic.timestamp}.json`,