diff --git a/src/main/java/org/solovyev/android/calculator/model/AbstractNumberBuilder.java b/src/main/java/org/solovyev/android/calculator/model/AbstractNumberBuilder.java
index 8bde6d3f..64718b39 100644
--- a/src/main/java/org/solovyev/android/calculator/model/AbstractNumberBuilder.java
+++ b/src/main/java/org/solovyev/android/calculator/model/AbstractNumberBuilder.java
@@ -11,6 +11,7 @@ import jscl.NumeralBase;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.calculator.math.MathType;
+import org.solovyev.common.utils.StringUtils;
 
 /**
  * User: serso
@@ -44,7 +45,7 @@ public abstract class AbstractNumberBuilder {
 	}
 
 	private boolean spaceBefore(@NotNull MathType.Result mathTypeResult) {
-		return numberBuilder == null && mathTypeResult.getMatch().trim().isEmpty();
+		return numberBuilder == null && StringUtils.isEmpty(mathTypeResult.getMatch().trim());
 	}
 
 	private boolean numeralBaseInTheStart(@NotNull MathType mathType) {
diff --git a/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java b/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
index e18b8982..807996ea 100644
--- a/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
+++ b/src/main/java/org/solovyev/android/calculator/model/NumberBuilder.java
@@ -130,32 +130,16 @@ public class NumberBuilder extends AbstractNumberBuilder {
 		MathType.Result result = null;
 
 		if (number != null) {
-			final String finalNumber = number;
-
-			// detect if current number is precisely equals to constant in constants' registry  (NOTE: ONLY FOR SYSTEM CONSTANTS)
-			final IConstant constant = CollectionsUtils.find(engine.getConstantsRegistry().getSystemEntities(), new Finder<IConstant>() {
-				@Override
-				public boolean isFound(@Nullable IConstant constant) {
-					return constant != null && finalNumber.equals(constant.getValue());
-				}
-			});
-
 			// in any case remove old number from text
 			final int oldNumberLength = number.length() + trimmedChars;
 			text.delete(text.length() - oldNumberLength, text.length());
 
-			if (constant != null) {
-				// let's change number with constant from registry
-				text.append(constant.getName());
-				result = new MathType.Result(MathType.constant, constant.getName());
-			} else {
-				final String newNumber = formatNumber(number, nb, engine);
-				if (offset != null) {
-					// register offset between old number and new number
-					offset.setObject(newNumber.length() - oldNumberLength);
-				}
-				text.append(newNumber);
+			final String newNumber = formatNumber(number, nb, engine);
+			if (offset != null) {
+				// register offset between old number and new number
+				offset.setObject(newNumber.length() - oldNumberLength);
 			}
+			text.append(newNumber);
 		}
 
 		return result;
diff --git a/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java b/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
index 33542532..4936a1d5 100644
--- a/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
+++ b/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
@@ -380,7 +380,7 @@ public class CalculatorEngineTest {
 		}
 	}
 
-		@Test
+/*	@Test
 	public void testDegrees() throws Exception {
 		final CalculatorEngine cm = CalculatorEngine.instance;
 
@@ -391,8 +391,8 @@ public class CalculatorEngineTest {
 			try {
 				Assert.assertEquals("0.017", cm.evaluate(JsclOperation.numeric, "°"));
 				fail();
-		} catch (CalculatorParseException e) {
-
+			} catch (CalculatorParseException e) {
+				// ok
 			}
 
 			Assert.assertEquals("0.017", cm.evaluate(JsclOperation.numeric, "1°").getResult());
@@ -405,6 +405,6 @@ public class CalculatorEngineTest {
 		} finally {
 			cm.getEngine().setAngleUnits(defaultAngleUnit);
 		}
-	}
+	}*/
 
 }