diff --git a/CHANGES/v2.4.md b/CHANGES/v2.4.md
index ae03f3e0e325d10354d2cbbf06871fda15262422..13c07a5b46a310c48baed82d8edc8a19c3241bf6 100644
--- a/CHANGES/v2.4.md
+++ b/CHANGES/v2.4.md
@@ -208,6 +208,7 @@ For users:
   - Updated NAMD patches to version 2.12 and 2.13. Old patches have been removed.
   - GROMACS patch for gromacs-2018.4.
   - Fixed a bug in CS2BACKBONE when using more than 2 chains
+  - Fixed a threadsafety issue using forces on histograms
 
 For developers:
   - All fixed done in version 2.3.8
diff --git a/src/analysis/Histogram.cpp b/src/analysis/Histogram.cpp
index 6631f35c91b5eabc7661f08495a6bc75f74bb37f..51b7ce478b936a0d50dcc84c4c31e81d1d4439bd 100644
--- a/src/analysis/Histogram.cpp
+++ b/src/analysis/Histogram.cpp
@@ -213,6 +213,7 @@ public:
   void prepareForAveraging();
   void performOperations( const bool& from_update );
   void finishAveraging();
+  bool threadSafe() const { return !in_apply; }
   bool isPeriodic() { return false; }
   unsigned getNumberOfDerivatives();
   void turnOnDerivatives();