diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a4a3bc176..6f95c9cdfe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Removed the deprecated `auth` endpoint of the login with _Security Token_ (`GET`)
 - Simplified the `getHistorical()` function response in the data provider interface
 
+### Fixed
+
+- Fixed the parsing of negative numbers in `extractNumberFromString()` (used by the manual data provider) which incorrectly dropped the minus sign
+
 ## 3.29.0 - 2026-07-18
 
 ### Added
diff --git a/libs/common/src/lib/helper.spec.ts b/libs/common/src/lib/helper.spec.ts
index 6a6fe47734..abac8acd57 100644
--- a/libs/common/src/lib/helper.spec.ts
+++ b/libs/common/src/lib/helper.spec.ts
@@ -43,6 +43,22 @@ describe('Helper', () => {
       ).toEqual(999.99);
     });
 
+    it('Get negative decimal number', () => {
+      expect(extractNumberFromString({ value: '-999.99' })).toEqual(-999.99);
+    });
+
+    it('Get negative decimal number (with currency)', () => {
+      expect(extractNumberFromString({ value: '-999.99 CHF' })).toEqual(
+        -999.99
+      );
+    });
+
+    it('Get negative decimal number with group (comma notation)', () => {
+      expect(
+        extractNumberFromString({ locale: 'de-DE', value: '-99.999,99' })
+      ).toEqual(-99999.99);
+    });
+
     it('Not a number', () => {
       expect(extractNumberFromString({ value: 'X' })).toEqual(NaN);
     });
diff --git a/libs/common/src/lib/helper.ts b/libs/common/src/lib/helper.ts
index 9a32927e23..30b0c2a680 100644
--- a/libs/common/src/lib/helper.ts
+++ b/libs/common/src/lib/helper.ts
@@ -210,8 +210,9 @@ export function extractNumberFromString({
   value: string;
 }): number | undefined {
   try {
-    // Remove non-numeric characters (excluding international formatting characters)
-    const numericValue = value.replace(/[^\d.,'’\s]/g, '');
+    // Remove non-numeric characters (excluding international formatting
+    // characters and the minus sign to preserve negative values)
+    const numericValue = value.replace(/[^\d.,'’\s-]/g, '');
 
     const parser = new NumberParser(locale);