diff --git a/core-common/src/main/java/org/glassfish/jersey/uri/internal/UriTemplateParser.java b/core-common/src/main/java/org/glassfish/jersey/uri/internal/UriTemplateParser.java
index b438023bf2..0f5f759ae5 100644
--- a/core-common/src/main/java/org/glassfish/jersey/uri/internal/UriTemplateParser.java
+++ b/core-common/src/main/java/org/glassfish/jersey/uri/internal/UriTemplateParser.java
@@ -395,9 +395,14 @@ private int parseName(final CharacterIterator ci, int skipGroup) {
                     //               groupCounts.add(1 + skipGroup);
 
                     if (variables.hasLength(0)) {
-                        int len = TEMPLATE_VALUE_PATTERN.pattern().length() - 1;
-                        String pattern = TEMPLATE_VALUE_PATTERN.pattern().substring(0, len) + '{' + variables.getLength(0) + '}';
-                        namePattern = Pattern.compile(pattern);
+                        if (variables.getLength(0) != 0) {
+                            int len = TEMPLATE_VALUE_PATTERN.pattern().length() - 1;
+                            String pattern = TEMPLATE_VALUE_PATTERN.pattern().substring(0, len)
+                                    + '{' + variables.getLength(0) + '}';
+                            namePattern = Pattern.compile(pattern);
+                        } else {
+                            namePattern = TEMPLATE_VALUE_PATTERN;
+                        }
                         templateVariable.setLength(variables.getLength(0));
                     } else {
                         namePattern = (!variables.hasRegexp(0))
@@ -462,7 +467,10 @@ private int parseName(final CharacterIterator ci, int skipGroup) {
                         if (argIndex != 0) {
                             regexBuilder.append(")");
                         }
-                        regexBuilder.append("{0,1}");
+
+                        if (!variables.hasRegexp(argIndex)) {
+                            regexBuilder.append("{0,1}");
+                        }
 
                         argIndex++;
                         groupCounts.add(2);
@@ -571,6 +579,7 @@ private void parse(CharacterIterator ci, String template) {
 
             StringBuilder regexBuilder = new StringBuilder();
             State state = State.TEMPLATE;
+            State previousState;
             boolean star = false;
             boolean whiteSpace = false;
             boolean ignoredLastComma = false;
@@ -579,6 +588,7 @@ private void parse(CharacterIterator ci, String template) {
             int regExpRound = 0;   // (
             boolean reqExpSlash = false; // \
             while ((state.value & (State.ERROR.value | State.EXIT.value)) == 0) {
+                previousState = state;
                 c = ci.next();
                 // "\\{(\\w[-\\w\\.]*)
                 if (Character.isLetterOrDigit(c)) {
@@ -702,8 +712,8 @@ private void parse(CharacterIterator ci, String template) {
                                 regexps.add(regex);
                             }
                         } else {
-                            regexps.add(null);
-                            lengths.add(null);
+                            regexps.add(previousState == State.REGEXP ? "" : null);
+                            lengths.add(previousState == State.REGEXP ? 0 : null);
                         }
 
                         names.add(nameBuilder.toString());
diff --git a/core-common/src/test/java/org/glassfish/jersey/uri/UriTemplateTest.java b/core-common/src/test/java/org/glassfish/jersey/uri/UriTemplateTest.java
index 7846c113af..cdd965bc9f 100644
--- a/core-common/src/test/java/org/glassfish/jersey/uri/UriTemplateTest.java
+++ b/core-common/src/test/java/org/glassfish/jersey/uri/UriTemplateTest.java
@@ -31,6 +31,8 @@
 
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
+import org.opentest4j.AssertionFailedError;
+
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -257,7 +259,7 @@ void _testMatching(final String template, final String uri, final String... valu
         final Map<String, String> m = new HashMap<String, String>();
 
         boolean isMatch = t.match(uri, m);
-        assertTrue(isMatch);
+        assertTrue(isMatch, "No match for '" + uri + "' & params '" + Arrays.toString(values) + "`");
         assertEquals(values.length, t.getTemplateVariables().size());
 
         final Iterator<String> names = t.getTemplateVariables().iterator();
@@ -982,6 +984,7 @@ void testRfc6570MultiplePathArgs() {
         _testTemplateNames("/{a,b,c}", "a", "b", "c");
         _testMatching("/uri/{a}", "/uri/hello", "hello");
         _testMatching("/uri/{a,b}", "/uri/hello,world", "hello", "world");
+        _testMatching("/uri/{a,b}", "/uri/x", "x", null);
         _testMatching("/uri{?a,b}", "/uri?a=hello&b=world", "hello", "world");
         _testMatching("/uri/{a,b,c}", "/uri/hello,world,!", "hello", "world", "!");
         _testMatching("/uri/{a,b,c}", "/uri/hello,world", "hello", "world", null);
@@ -989,6 +992,12 @@ void testRfc6570MultiplePathArgs() {
         _testMatching("/uri/{a,b,c}", "/uri/", null, null, null);
     }
 
+    @Test
+    public void testRegularExpressionIsNotOptional() {
+        Assertions.assertThrows(AssertionFailedError.class,
+                () -> _testMatching("/{name: [a-z0-9]{3,128}}", "/", new String[]{null}));
+    }
+
     @Test
     void testRfc6570PathLength() {
         _testMatching("/uri/{a:5}", "/uri/hello", "hello");