diff --git a/src/nt/ntutils.cpp b/src/nt/ntutils.cpp
index 5e244af..858163a 100644
--- a/src/nt/ntutils.cpp
+++ b/src/nt/ntutils.cpp
@@ -14,12 +14,15 @@ namespace epics { namespace nt {
 
 bool NTUtils::is_a(const std::string &u1, const std::string &u2)
 {
-    // remove minor for the u2
-    size_t pos = u2.find_last_of('.');
-    std::string su2 = (pos == string::npos) ? u2 : u2.substr(0, pos);
+    // remove minor for the u1
+    size_t pos1 = u1.find_last_of('.');
+    std::string su1 = (pos1 == string::npos) ? u1 : u1.substr(0, pos1);
 
-    // "starts with comparison"
-    return su2.size() <= u1.size() && u1.compare(0, su2.size(), su2) == 0;
+    // remove minor for the u2
+    size_t pos2 = u2.find_last_of('.');
+    std::string su2 = (pos2 == string::npos) ? u2 : u2.substr(0, pos2);
+
+    return su2 == su1;
 }
 
 }}
diff --git a/test/nt/ntutilsTest.cpp b/test/nt/ntutilsTest.cpp
index cc57ddc..30ef656 100644
--- a/test/nt/ntutilsTest.cpp
+++ b/test/nt/ntutilsTest.cpp
@@ -24,11 +24,13 @@ void test_is_a()
     testOk1(!NTUtils::is_a("epics:nt/NTTable:1.0", "epics:nt/NTTable:2.0"));
     testOk1(!NTUtils::is_a("epics:nt/NTTable:2.0", "epics:nt/NTTable:1.0"));
     testOk1(!NTUtils::is_a("epics:nt/NTTable:1.3", "epics:nt/NTTable:2.3"));
+    testOk1(!NTUtils::is_a("epics:nt/NTTable:1.0", "epics:nt/NTTable:11.0"));
+    testOk1(!NTUtils::is_a("epics:nt/NTTable:11.0", "epics:nt/NTTable:1.0"));
     testOk1(!NTUtils::is_a("epics:nt/NTTable:1.0", "epics:nt/NTMatrix:1.0"));
 }
 
 MAIN(testNTUtils) {
-    testPlan(8);
+    testPlan(10);
     test_is_a();
     return testDone();
 }