diff --git a/cxx-squid/src/main/java/org/sonar/cxx/preprocessor/CxxPreprocessor.java b/cxx-squid/src/main/java/org/sonar/cxx/preprocessor/CxxPreprocessor.java
index d9d4a76ed9..ca978f2c71 100644
--- a/cxx-squid/src/main/java/org/sonar/cxx/preprocessor/CxxPreprocessor.java
+++ b/cxx-squid/src/main/java/org/sonar/cxx/preprocessor/CxxPreprocessor.java
@@ -860,6 +860,22 @@ private Token predConcatToken(List<Token> tokens) {
     while (!tokens.isEmpty()) {
       Token last = tokens.remove(tokens.size() - 1);
       if (last.getType() != WS) {
+        if ( !tokens.isEmpty() ) {
+          Token pred = tokens.get(tokens.size() - 1);
+          if (pred.getType() != WS && !pred.hasTrivia()) {
+            // Needed to paste tokens 0 and x back together after #define N(hex) 0x ## hex
+            tokens.remove(tokens.size() - 1);
+            String replacement = pred.getValue() + last.getValue();
+            last = Token.builder()
+                .setLine(pred.getLine())
+                .setColumn(pred.getColumn())
+                .setURI(pred.getURI())
+                .setValueAndOriginalValue(replacement)
+                .setType(pred.getType())
+                .setGeneratedCode(true)
+                .build();
+          }
+        }
         return last;
       }
     }
diff --git a/cxx-squid/src/test/java/org/sonar/cxx/parser/PreprocessorDirectivesTest.java b/cxx-squid/src/test/java/org/sonar/cxx/parser/PreprocessorDirectivesTest.java
index eb96d4d535..098039ee18 100644
--- a/cxx-squid/src/test/java/org/sonar/cxx/parser/PreprocessorDirectivesTest.java
+++ b/cxx-squid/src/test/java/org/sonar/cxx/parser/PreprocessorDirectivesTest.java
@@ -61,19 +61,15 @@ public void preprocessorDirectives() {
 
   @Test
   public void hashhash_related_parsing_problem() {
-    // TODO: make it run.
-    // this reproduces a macros expansion problem where
-    // whitespace handling goes wrong
-
-    // assertThat(p).matches(
-    //   "#define CASES CASE(00)\n"
-    //   + "#define CASE(n) case 0x##n:\n"
-    //   + "void foo()  {\n"
-    //   + "switch (1) {\n"
-    //   + "CASES\n"
-    //   + "break;\n"
-    //   + "}\n"
-    //   + "}\n");
+     assertThat(p).matches(
+       "#define CASES CASE(00)\n"
+       + "#define CASE(n) case 0x##n:\n"
+       + "void foo()  {\n"
+       + "switch (1) {\n"
+       + "CASES\n"
+       + "break;\n"
+       + "}\n"
+       + "}\n");
   }
 
   @Test
@@ -261,13 +257,11 @@ public void concatenation() {
       + "macro_start"))
       .equals("int main ( void ) ; EOF"));
 
-    // FIXME: this failes due to a bug in production code
-    // which rips apart the number '0xcf'
-    // assert (serialize(p.parse(
-    //   "#define A B(cf)\n"
-    //   + "#define B(n) 0x##n\n"
-    //   + "i = A;"))
-    //   .equals("i = 0xcf ; EOF"));
+    assert (serialize(p.parse(
+      "#define A B(cf)\n"
+      + "#define B(n) 0x##n\n"
+      + "i = A;"))
+      .equals("i = 0xcf ; EOF"));
   }
 
   @Test