diff --git a/prism/src/prism/PrismUtils.java b/prism/src/prism/PrismUtils.java
index 11e28efa..821d7a94 100644
--- a/prism/src/prism/PrismUtils.java
+++ b/prism/src/prism/PrismUtils.java
@@ -60,7 +60,7 @@ public class PrismUtils
 	
 	public static double log(double x, double b)
 	{
-		// If base is <0 or ==1 (or +Inf/NaN), then result is NaN
+		// If base is <=0 or ==1 (or +Inf/NaN), then result is NaN
 		if (b <= 0 || b == 1 || (Double.isInfinite(b)) || Double.isNaN(b)) return Double.NaN;
 		
 		// Otherwise, log_b (x) is log(x) / log(b)
diff --git a/prism/src/simulator/simexpression.cc b/prism/src/simulator/simexpression.cc
index 0aee9057..ed5bd359 100644
--- a/prism/src/simulator/simexpression.cc
+++ b/prism/src/simulator/simexpression.cc
@@ -1410,8 +1410,8 @@ double CLog::EvaluateDouble()
 		base = rexpr->Evaluate();
 	else
 		base = rexpr->EvaluateDouble();
-	// If base is <0 or ==1 (or +Inf/NaN), then result is NaN
-	if (base < 0 || base == 1.0 || base == HUGE_VAL || base != base) { res = 0.0; res /= res; }
+	// If base is <=0 or ==1 (or +Inf/NaN), then result is NaN
+	if (base <= 0 || base == 1.0 || base == HUGE_VAL || base != base) { res = 0.0; res /= res; }
 	// If arg is <0 or NaN, then result is NaN
 	else if (val < 0 || val != val) { res = 0.0; res /= res; }
 	// If arg is +Inf, then result is +Inf