diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx14/constexpr/FloatingPointValueTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx14/constexpr/FloatingPointValueTests.java
index d17f8b3b7ed..2727a202128 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx14/constexpr/FloatingPointValueTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx14/constexpr/FloatingPointValueTests.java
@@ -39,6 +39,11 @@ public class FloatingPointValueTests extends TestBase {
 		assertEvaluationEquals(2.5);
 	}
 
+	//	constexpr auto x = -2.5;
+	public void testNegativeDoubleLiteral() throws Exception {
+		assertEvaluationEquals(-2.5);
+	}
+
 	//  constexpr auto x = .5f;
 	public void testFloatLiteral() throws Exception {
 		assertEvaluationEquals(0.5);
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/FloatingPointValue.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/FloatingPointValue.java
index fb792fe96d4..a0837864035 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/FloatingPointValue.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/FloatingPointValue.java
@@ -44,6 +44,12 @@ public final class FloatingPointValue implements IValue {
 		int i = 0;
 		int len = value.length;
 
+		boolean valueIsPositive = true;
+		if (i < len && (value[i] == '+' || value[i] == '-')) {
+			valueIsPositive = (value[i] == '+');
+			++i;
+		}
+
 		while (i < len && value[i] >= '0' && value[i] <= '9') {
 			int digit = value[i] - '0';
 			result = result * 10 + digit;
@@ -87,6 +93,9 @@ public final class FloatingPointValue implements IValue {
 			if (!exponentIsPositive) {
 				exponent *= -1;
 			}
+			if (!valueIsPositive) {
+				result *= -1;
+			}
 			return result * Math.pow(10, exponent);
 		}
 		return null;