diff --git a/lib/suppressions.cpp b/lib/suppressions.cpp
index d22f4415c..899455bd7 100644
--- a/lib/suppressions.cpp
+++ b/lib/suppressions.cpp
@@ -224,7 +224,7 @@ std::string Suppressions::addSuppression(const std::string &errorId, const std::
     }
     if (errorId != "*") {
         for (std::string::size_type pos = 0; pos < errorId.length(); ++pos) {
-            if (errorId[pos] < 0 || !std::isalnum(errorId[pos])) {
+            if (errorId[pos] < 0 || (!std::isalnum(errorId[pos]) &&  errorId[pos] != '_')) {
                 return "Failed to add suppression. Invalid id \"" + errorId + "\"";
             }
             if (pos == 0 && std::isdigit(errorId[pos])) {
diff --git a/test/testsuppressions.cpp b/test/testsuppressions.cpp
index f86433866..91e27c5f0 100644
--- a/test/testsuppressions.cpp
+++ b/test/testsuppressions.cpp
@@ -45,8 +45,11 @@ private:
 
     void suppressionsBadId1() {
         Suppressions suppressions;
-        std::istringstream s("123");
-        ASSERT_EQUALS("Failed to add suppression. Invalid id \"123\"", suppressions.parseFile(s));
+        std::istringstream s1("123");
+        ASSERT_EQUALS("Failed to add suppression. Invalid id \"123\"", suppressions.parseFile(s1));
+
+        std::istringstream s2("obsoleteFunctionsrand_r");
+        ASSERT_EQUALS("", suppressions.parseFile(s2));
     }
 
     void suppressionsDosFormat() {