diff --git a/include/light/ltface.hh b/include/light/ltface.hh
index 7c7320d3..ffe634c3 100644
--- a/include/light/ltface.hh
+++ b/include/light/ltface.hh
@@ -72,6 +72,7 @@ struct lightgrid_sample_t
      * - if a color component is nan, nan is considered equal to nan for the purposes of this comparison
      */
     bool operator==(const lightgrid_sample_t &other) const;
+    bool operator!=(const lightgrid_sample_t &other) const; //gcc9 workaround
 };
 
 struct lightgrid_samples_t
diff --git a/light/ltface.cc b/light/ltface.cc
index 0b3591be..951dda62 100644
--- a/light/ltface.cc
+++ b/light/ltface.cc
@@ -3580,6 +3580,11 @@ bool lightgrid_sample_t::operator==(const lightgrid_sample_t &other) const
     return true;
 }
 
+bool lightgrid_sample_t::operator!=(const lightgrid_sample_t &other) const
+{
+    return !(*this == other);
+}
+
 int lightgrid_samples_t::used_styles() const
 {
     int used = 0;