diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/scanner2/Scanner2Test.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/scanner2/Scanner2Test.java
index edbcfac0746..c3366b0967b 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/scanner2/Scanner2Test.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/scanner2/Scanner2Test.java
@@ -2665,4 +2665,16 @@ public class Scanner2Test extends BaseScanner2Test
        validateToken( IToken.tRPAREN );
        validateChar( "s" );
    }
+   
+   public void testBug185120() throws Exception {
+       StringBuffer buffer = new StringBuffer();
+       buffer.append("#define TEST_DEFINE 1UL\n"); 
+       buffer.append("#if TEST_DEFINE != 1UL\n"); 
+       buffer.append("-\n"); 
+       buffer.append("#else\n"); 
+       buffer.append("+\n"); 
+       buffer.append("#endif\n"); 
+       initializeScanner( buffer.toString() );
+       validateToken( IToken.tPLUS );
+   }
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/ExpressionEvaluator.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/ExpressionEvaluator.java
index 0dd6408838e..705574c3cd0 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/ExpressionEvaluator.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/parser/scanner2/ExpressionEvaluator.java
@@ -618,7 +618,13 @@ public class ExpressionEvaluator {
                     // end of number
                     if (c == 'L' || c == 'l' || c == 'U' || c == 'u') {
                         // eat the long/unsigned
-                        ++bufferPos[bufferStackPos];
+                    	int pos= ++bufferPos[bufferStackPos];
+                    	if (pos < limit) {
+                    		c= buffer[pos];
+                    		if (c == 'L' || c == 'l' || c == 'U' || c == 'u') {
+                    			++bufferPos[bufferStackPos];
+                    		}
+                    	}
                     }
 
                     // done