diff --git a/bounds.patch b/bounds.patch
new file mode 100644
index 00000000..461d9ec4
--- /dev/null
+++ b/bounds.patch
@@ -0,0 +1,79 @@
+diff --git a/src/main/java/net/imglib2/roi/Bounds.java b/src/main/java/net/imglib2/roi/Bounds.java
+index 3f9e1ab..7c5145b 100644
+--- a/src/main/java/net/imglib2/roi/Bounds.java
++++ b/src/main/java/net/imglib2/roi/Bounds.java
+@@ -535,40 +535,60 @@ public abstract class Bounds< I extends RealInterval, B extends Bounds< I, B > >
+ 
+ 		private final RealInterval i2;
+ 
++		private final double[] min;
++
++		private final double[] max;
++
+ 		public UnionRealInterval( final RealInterval i1, final RealInterval i2 )
+ 		{
+ 			super( i1.numDimensions() );
+ 			this.i1 = i1;
+ 			this.i2 = i2;
+ 			assert ( i1.numDimensions() == i2.numDimensions() );
++			min = new double[ i1.numDimensions() ];
++			max = new double[ i1.numDimensions() ];
++			Arrays.fill( min, Double.NaN );
++			Arrays.fill( max, Double.NaN );
+ 		}
+ 
+ 		@Override
+ 		public double realMin( final int d )
+ 		{
+-			if ( Intervals.isEmpty( i1 ) )
++			if ( Double.isNaN( min[ d ] ) )
+ 			{
+-				if ( Intervals.isEmpty( i2 ) )
+-					return Double.POSITIVE_INFINITY;
+-				return i2.realMin( d );
++				if ( Intervals.isEmpty( i1 ) )
++				{
++					if ( Intervals.isEmpty( i2 ) )
++						min[ d ] = Double.POSITIVE_INFINITY;
++					else
++						min[ d ] = i2.realMin( d );
++				}
++				else if ( Intervals.isEmpty( i2 ) )
++					min[ d] = i1.realMin( d );
++				else
++					min[ d ] = Math.min( i1.realMin( d ), i2.realMin( d ) );
+ 			}
+-			if ( Intervals.isEmpty( i2 ) )
+-				return i1.realMin( d );
+-			return Math.min( i1.realMin( d ), i2.realMin( d ) );
++			return min[ d ];
+ 		}
+ 
+ 		@Override
+ 		public double realMax( final int d )
+ 		{
+-			if ( Intervals.isEmpty( i1 ) )
++			if ( Double.isNaN( max[d] )
+ 			{
+-				if ( Intervals.isEmpty( i2 ) )
+-					return Double.NEGATIVE_INFINITY;
+-				return i2.realMax( d );
++				if ( Intervals.isEmpty( i1 ) )
++				{
++					if ( Intervals.isEmpty( i2 ) )
++						max[ d ] = Double.NEGATIVE_INFINITY;
++					else
++						max[ d ] = i2.realMax( d );
++				}
++				else if ( Intervals.isEmpty( i2 ) )
++					max[ d ] = i1.realMax( d );
++				else
++					max[ d ] = Math.max( i1.realMax( d ), i2.realMax( d ) );
+ 			}
+-			if ( Intervals.isEmpty( i2 ) )
+-				return i1.realMax( d );
+-			return Math.max( i1.realMax( d ), i2.realMax( d ) );
++			return max[ d ];
+ 		}
+ 	}
+
diff --git a/src/main/java/net/imglib2/roi/Bounds.java b/src/main/java/net/imglib2/roi/Bounds.java
index 3f9e1abb..869a8aa9 100644
--- a/src/main/java/net/imglib2/roi/Bounds.java
+++ b/src/main/java/net/imglib2/roi/Bounds.java
@@ -535,40 +535,60 @@ public static class UnionRealInterval extends AbstractAdaptingRealInterval
 
 		private final RealInterval i2;
 
+		private final double[] min;
+
+		private final double[] max;
+
 		public UnionRealInterval( final RealInterval i1, final RealInterval i2 )
 		{
 			super( i1.numDimensions() );
 			this.i1 = i1;
 			this.i2 = i2;
 			assert ( i1.numDimensions() == i2.numDimensions() );
+			min = new double[ i1.numDimensions() ];
+			max = new double[ i1.numDimensions() ];
+			Arrays.fill( min, Double.NaN );
+			Arrays.fill( max, Double.NaN );
 		}
 
 		@Override
 		public double realMin( final int d )
 		{
-			if ( Intervals.isEmpty( i1 ) )
+			if ( Double.isNaN( min[ d ] ) )
 			{
-				if ( Intervals.isEmpty( i2 ) )
-					return Double.POSITIVE_INFINITY;
-				return i2.realMin( d );
+				if ( Intervals.isEmpty( i1 ) )
+				{
+					if ( Intervals.isEmpty( i2 ) )
+						min[ d ] = Double.POSITIVE_INFINITY;
+					else
+						min[ d ] = i2.realMin( d );
+				}
+				else if ( Intervals.isEmpty( i2 ) )
+					min[ d] = i1.realMin( d );
+				else
+					min[ d ] = Math.min( i1.realMin( d ), i2.realMin( d ) );
 			}
-			if ( Intervals.isEmpty( i2 ) )
-				return i1.realMin( d );
-			return Math.min( i1.realMin( d ), i2.realMin( d ) );
+			return min[ d ];
 		}
 
 		@Override
 		public double realMax( final int d )
 		{
-			if ( Intervals.isEmpty( i1 ) )
+			if ( Double.isNaN( max[d] ) )
 			{
-				if ( Intervals.isEmpty( i2 ) )
-					return Double.NEGATIVE_INFINITY;
-				return i2.realMax( d );
+				if ( Intervals.isEmpty( i1 ) )
+				{
+					if ( Intervals.isEmpty( i2 ) )
+						max[ d ] = Double.NEGATIVE_INFINITY;
+					else
+						max[ d ] = i2.realMax( d );
+				}
+				else if ( Intervals.isEmpty( i2 ) )
+					max[ d ] = i1.realMax( d );
+				else
+					max[ d ] = Math.max( i1.realMax( d ), i2.realMax( d ) );
 			}
-			if ( Intervals.isEmpty( i2 ) )
-				return i1.realMax( d );
-			return Math.max( i1.realMax( d ), i2.realMax( d ) );
+			return max[ d ];
 		}
 	}
 
diff --git a/src/test/java/net/imglib2/roi/GeomMaskMultipleORTest.java b/src/test/java/net/imglib2/roi/GeomMaskMultipleORTest.java
index 17ddbb2c..fb061ce2 100644
--- a/src/test/java/net/imglib2/roi/GeomMaskMultipleORTest.java
+++ b/src/test/java/net/imglib2/roi/GeomMaskMultipleORTest.java
@@ -3,6 +3,8 @@
 import net.imglib2.roi.geom.GeomMasks;
 import org.junit.Test;
 
+import static org.junit.Assert.assertTrue;
+
 public class GeomMaskMultipleORTest
 {
 	@Test
@@ -11,13 +13,16 @@ public void multipleOr()
 		final RealMaskRealInterval mask = GeomMasks.closedBox( new double[]{ 0, 0, 0 }, new double[]{ 1, 1, 1 } );
 		RealMaskRealInterval test = mask;
 		long start = System.currentTimeMillis();
+		long duration = 0;
 		for ( int i = 0; i < 20; i++ )
 		{
 			test = test.or( mask );
 			System.out.println( "RealMin: " + test.realMin( 0 ));
 			System.out.println( "NumOr: " + i );
-			System.out.println( "Duration [ms]:" + ( System.currentTimeMillis() - start ) );
+			duration = System.currentTimeMillis() - start;
+			System.out.println( "Duration [ms]: " + duration );
 			start = System.currentTimeMillis();
 		}
+		assertTrue( duration < 10 );
 	}
 }