diff --git a/src/gtk/window.cpp b/src/gtk/window.cpp
index 0be16df1c9..3f5d2adf95 100644
--- a/src/gtk/window.cpp
+++ b/src/gtk/window.cpp
@@ -4601,7 +4601,9 @@ int wxWindowGTK::GetScrollRange( int orient ) const
 //   difference due to possible inexactness in floating point arithmetic
 static inline bool IsScrollIncrement(double increment, double x)
 {
-    wxASSERT(increment > 0);
+    wxASSERT(increment >= 0);
+    if ( increment == 0. )
+        return false;
     const double tolerance = 1.0 / 1024;
     return fabs(increment - fabs(x)) < tolerance;
 }