diff --git a/packages/@n8n/utils/src/format-pem-block.test.ts b/packages/@n8n/utils/src/format-pem-block.test.ts
index d873d563b37..e7d48ee1896 100644
--- a/packages/@n8n/utils/src/format-pem-block.test.ts
+++ b/packages/@n8n/utils/src/format-pem-block.test.ts
@@ -34,6 +34,12 @@ ABC
 		expect(formatPemBlock('')).toBe('');
 	});
 
+	it('should return non-PEM input unchanged', () => {
+		expect(formatPemBlock('my secret key')).toBe('my secret key');
+		expect(formatPemBlock('pass\\nphrase')).toBe('pass\\nphrase');
+		expect(formatPemBlock('-----END CERTIFICATE-----')).toBe('-----END CERTIFICATE-----');
+	});
+
 	it('should format compact RSA PRIVATE KEY block', () => {
 		const compactKey = `-----BEGIN RSA PRIVATE KEY-----${'C'.repeat(64)}-----END RSA PRIVATE KEY-----`;
 
diff --git a/packages/@n8n/utils/src/format-pem-block.ts b/packages/@n8n/utils/src/format-pem-block.ts
index fee99a7105d..d61732c8603 100644
--- a/packages/@n8n/utils/src/format-pem-block.ts
+++ b/packages/@n8n/utils/src/format-pem-block.ts
@@ -25,6 +25,9 @@ function formatCompactPem(pem: string, isPublic: boolean): string | undefined {
  * by collapsing whitespace and wrapping the body at 64 chars. Multi-block PEM
  * chains are returned unchanged.
  *
+ * Input that is not a single-line PEM block is returned unchanged, so a plain
+ * secret (e.g. a key passphrase) passed here by mistake is not corrupted.
+ *
  * @param pem - The PEM-encoded block to format.
  * @param isPublic - When true, match `PUBLIC KEY` labels instead of the default `PRIVATE KEY` / `CERTIFICATE`.
  * @returns The formatted PEM block.
@@ -34,7 +37,9 @@ export function formatPemBlock(pem: string, isPublic = false): string {
 	if (isPublic) {
 		regex = /(PUBLIC KEY)/;
 	}
-	if (!pem || /\n/.test(pem)) {
+	// The fallback formatter below would collapse a non-PEM value's whitespace
+	// into newlines, corrupting plain secrets such as key passphrases.
+	if (!pem || /\n/.test(pem) || !pem.includes('-----BEGIN ')) {
 		return pem;
 	}
 	const compactPem = formatCompactPem(pem, isPublic);
diff --git a/packages/nodes-base/nodes/HttpRequest/GenericFunctions.ts b/packages/nodes-base/nodes/HttpRequest/GenericFunctions.ts
index 30926c657bc..c4dbf0dd0ad 100644
--- a/packages/nodes-base/nodes/HttpRequest/GenericFunctions.ts
+++ b/packages/nodes-base/nodes/HttpRequest/GenericFunctions.ts
@@ -312,8 +312,7 @@ export const setAgentOptions = (
 		if (sslCertificates.ca) agentOptions.ca = formatPemBlock(sslCertificates.ca);
 		if (sslCertificates.cert) agentOptions.cert = formatPemBlock(sslCertificates.cert);
 		if (sslCertificates.key) agentOptions.key = formatPemBlock(sslCertificates.key);
-		if (sslCertificates.passphrase)
-			agentOptions.passphrase = formatPemBlock(sslCertificates.passphrase);
+		if (sslCertificates.passphrase) agentOptions.passphrase = sslCertificates.passphrase;
 		requestOptions.agentOptions = agentOptions;
 	}
 };
diff --git a/packages/nodes-base/nodes/HttpRequest/test/utils/utils.test.ts b/packages/nodes-base/nodes/HttpRequest/test/utils/utils.test.ts
index e66687d6333..d2642183120 100644
--- a/packages/nodes-base/nodes/HttpRequest/test/utils/utils.test.ts
+++ b/packages/nodes-base/nodes/HttpRequest/test/utils/utils.test.ts
@@ -131,6 +131,48 @@ describe('HTTP Node Utils', () => {
 				},
 			});
 		});
+
+		it('should keep a passphrase containing whitespace unchanged', async () => {
+			const requestOptions: IRequestOptions = {
+				method: 'GET',
+				uri: 'https://example.com',
+			};
+
+			const sslCertificates = {
+				passphrase: 'my secret key',
+			};
+
+			setAgentOptions(requestOptions, sslCertificates);
+
+			expect(requestOptions).toStrictEqual({
+				method: 'GET',
+				uri: 'https://example.com',
+				agentOptions: {
+					passphrase: 'my secret key',
+				},
+			});
+		});
+
+		it('should wrap compact PEM certificates but not the passphrase', async () => {
+			const requestOptions: IRequestOptions = {
+				method: 'GET',
+				uri: 'https://example.com',
+			};
+
+			const sslCertificates = {
+				cert: `-----BEGIN CERTIFICATE-----${'A'.repeat(70)}-----END CERTIFICATE-----`,
+				key: `-----BEGIN PRIVATE KEY-----${'B'.repeat(70)}-----END PRIVATE KEY-----`,
+				passphrase: 'my secret key',
+			};
+
+			setAgentOptions(requestOptions, sslCertificates);
+
+			expect(requestOptions.agentOptions).toStrictEqual({
+				cert: `-----BEGIN CERTIFICATE-----\n${'A'.repeat(64)}\n${'A'.repeat(6)}\n-----END CERTIFICATE-----`,
+				key: `-----BEGIN PRIVATE KEY-----\n${'B'.repeat(64)}\n${'B'.repeat(6)}\n-----END PRIVATE KEY-----`,
+				passphrase: 'my secret key',
+			});
+		});
 	});
 
 	describe('sanitizeUiMessage', () => {