diff --git a/c/common/src/codingstandards/c/Identifiers.qll b/c/common/src/codingstandards/c/Identifiers.qll
index c100747cfb..580cd8cfdd 100644
--- a/c/common/src/codingstandards/c/Identifiers.qll
+++ b/c/common/src/codingstandards/c/Identifiers.qll
@@ -12,5 +12,8 @@ class InterestingIdentifiers extends Declaration {
     exists(this.getADeclarationLocation())
   }
 
-  string getSignificantName() { result = this.getName().prefix(31) }
+  //this definition of significant relies on the number of significant characters for a macro name (C99)
+  //this is used on macro name comparisons only
+  //not necessarily against other types of identifiers
+  string getSignificantNameComparedToMacro() { result = this.getName().prefix(63) }
 }
diff --git a/c/misra/src/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.ql b/c/misra/src/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.ql
index ff0b730e1f..2ee6ef26d2 100644
--- a/c/misra/src/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.ql
+++ b/c/misra/src/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.ql
@@ -22,10 +22,12 @@ where
   not isExcluded(i, Declarations3Package::identifiersNotDistinctFromMacroNamesQuery()) and
   mName = iName and
   (
-    //C99 states the first 31 characters of external identifiers are significant
-    //C90 states the first 6 characters of external identifiers are significant and case is not required to be significant
+    //C99 states the first 63 characters of macro identifiers are significant
+    //C90 states the first 31 characters of macro identifiers are significant
     //C90 is not currently considered by this rule
-    if m.getName().length() > 31 then mName = m.getName().prefix(31) else mName = m.getName()
+    if m.getName().length() > 63 then mName = m.getName().prefix(63) else mName = m.getName()
   ) and
-  if i.getName().length() > 31 then iName = i.getSignificantName() else iName = i.getName()
+  if i.getName().length() > 63
+  then iName = i.getSignificantNameComparedToMacro()
+  else iName = i.getName()
 select m, "Macro name is nonunique compared to $@.", i, i.getName()
diff --git a/c/misra/test/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.expected b/c/misra/test/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.expected
index bf8cf218d8..5874d1f6f5 100644
--- a/c/misra/test/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.expected
+++ b/c/misra/test/rules/RULE-5-5/IdentifiersNotDistinctFromMacroNames.expected
@@ -1,2 +1,2 @@
 | test.c:1:1:1:23 | #define Sum(x,y) x + y | Macro name is nonunique compared to $@. | test.c:4:5:4:7 | Sum | Sum |
-| test.c:6:1:6:42 | #define iltiqzxgfqsgigwfuyntzghvzltueeaZ ; | Macro name is nonunique compared to $@. | test.c:7:12:7:43 | iltiqzxgfqsgigwfuyntzghvzltueeaQ | iltiqzxgfqsgigwfuyntzghvzltueeaQ |
+| test.c:6:1:6:72 | #define iltiqzxgfqsgigwfuyntzghvzltueatcxqnqofnnvjyszmcsylyohvqaosjbqyyA | Macro name is nonunique compared to $@. | test.c:11:5:11:68 | iltiqzxgfqsgigwfuyntzghvzltueatcxqnqofnnvjyszmcsylyohvqaosjbqyyB | iltiqzxgfqsgigwfuyntzghvzltueatcxqnqofnnvjyszmcsylyohvqaosjbqyyB |
diff --git a/c/misra/test/rules/RULE-5-5/test.c b/c/misra/test/rules/RULE-5-5/test.c
index 6ae5c4c871..914c42386d 100644
--- a/c/misra/test/rules/RULE-5-5/test.c
+++ b/c/misra/test/rules/RULE-5-5/test.c
@@ -3,5 +3,12 @@
 
 int Sum;
 
-#define iltiqzxgfqsgigwfuyntzghvzltueeaZ ;   // NON_COMPLIANT - length 32
-static int iltiqzxgfqsgigwfuyntzghvzltueeaQ; // NON_COMPLIANT - length 32
\ No newline at end of file
+#define iltiqzxgfqsgigwfuyntzghvzltueatcxqnqofnnvjyszmcsylyohvqaosjbqyyA // NON_COMPLIANT
+                                                                         // -
+                                                                         // length
+                                                                         // 64
+static int
+    iltiqzxgfqsgigwfuyntzghvzltueatcxqnqofnnvjyszmcsylyohvqaosjbqyyB; // NON_COMPLIANT
+                                                                      // -
+                                                                      // length
+                                                                      // 64
\ No newline at end of file